Overview
I've been playing this for a week now and having a lot of fun - it keeps drawing me back in.
This is my first foray into Massively Multiplayer Online RPGs, and I do very little computer gaming in general, but I have plenty of time right now as I'm underemployed, and Amazon UK had a good price. After fairly intensive playing I have two characters at level 9 and one about to hit level 6. Experienced MMORPGamers might scoff at the pace of this, but there was a learning curve (and still is!), and I prefer to treat it as an experience rather than a race. (If anyone comes across The Black Spot or Steppehowler on Defiant or Shockbolt on Union feel free to say hi!) That means I can't comment on new goodies that might become available at higher levels.

Steppehowler (front) and team clearing villains from a hideout
I saw an online review (don't remember where now) that summed CoH up very well as punching people in the face while looking cool. As an attempt at the supers genre it gives you plenty of options for powers and costume, then sends you out to beat up bad guys. In that, it does pretty well. The visuals of the characters, powers and scenery are very good, and it's probably as close as you're going to get to the feeling of "I just encased that villain in a block of ice/set fire to his whiskers/knocked him flying". Sound's good too - for instance Steppehowler is heavy-built, and the sound when he lands from a jump or walks on metal steps is different than for a lighter character.
However, that's really all it's about. I was cautioned by a friend that I might lose interest pretty quickly because of the lack of depth. I see what he meant, though I think I might last longer than he did. All the character advancement options are about improving your powers or appearance, and all the action is about finding new bad guys and socking them. I think the key, as with most games, is to have a good awareness of what it is and not criticise it for failing to be what you wish it would be.
I also get an impression that - again, like many tabletop RPGs - it was rushed to release a bit. Small things that aren't quite smoothed out yet. I don't know whether this was deliberate, but the UK release was just before the schools broke up for half-term week. It would certainly be savvy marketing: parents with offspring to occupy, teenage boys (mostly) keen to smite things with their mates. There certainly seem to be plenty of teenagers online, happy just larking about. (And younger - at one point I tried to start a conversation with a character and after a pause got back "this player is 6 years old, just having fun - dad typing", which I thought was great.)
The main issue is the documentation. The UK box comes with a short quickstart booklet that gets you going but doesn't explain lots of stuff. My friend had a US box, and he got quite a thick little book. This seems to be available on the website as a 79MB download. Normally you'd expect it to be included on the game DVD as reference, but it isn't. The in-game help function is sometimes useful, but more often it's "Kindly explain your explanation."
Occasionally names of things are different in different places. Paragon City (where it all goes down) is divided into a number of zones, each with its own character and look. These are named differently on the paper map that comes with the box than in the game itself - mostly because residents always refer to them by a nickname rather than their official one, but it's still confusing. (The city has undergone many upheavals, including a major alien invasion, and some zones got pretty busted up and overrun by nasties, leading to changes like Eastgate getting called The Hollows.)
Each area also has a different level of danger, and it's not always clear in advance what this will be. I went exploring a new area and got demolished by street thugs a short way in. When this happens you get teleported to the nearest hospital. In this case the hospital was well inside the zone, and I was unable to get back to the gate in one piece to get out again. After several attempts I shouted till someone of higher level came to help, but that took a while and if no-one had answered I would have been stuck, which seems a bit like bad design. This led to a golden rule: when entering a new zone on your own, check out the first group of street thugs you see from a great distance; if they're coded red or purple, turn right round and go back out again!
There seems to be an ongoing issue with server lag, even though the loads are rated light. Given that so much of the game revolves around the speed and chaos of combat, this tends to annoy people. It's hard to target opponents when they're jumping around the screen and your powers aren't responding. Most of the time there's no problem, but it happens often enough to be noticeable.
Character creation
Characters are defined very simply. You don't have access to underlying attributes, and there's no place for skills in the game. Everything you do is about your powers.
The basis of the character is the choice of origin and archetype. Origin is how you got your powers: technology, mutation, magic, etc. It seems to make very little difference, affecting only your starting choice of missions and where you can get more effective power boosts at higher levels. I might have missed something. Archetype is the biggy. Heroes can be Blasters, Controllers, Defenders, Scrappers or Tankers. This sets the underlying attributes for combat prowess and soaking up damage, and determines the power sets you can access. A Blaster can do good damage with ranged attacks but is easily taken out if foes get into hand-to-hand range; a Scrapper is maximised for close combat but can't do anything at range. The archetypes are there to assign roles within a team - the Defender, for instance, focuses on strengthening other characters and weakening foes - and some do better at solo work than others (or, at least, require different strategies - a Blaster has to be much more cautious than a Scrapper, backing off rather than wading in).
Power sets are lists of powers with the same theme. For instance Electricity Manipulation's first two are throwing an immobilising electric "fence" round an enemy and wrapping your fists in electricity for a punch. Your archetype determines the options from which you choose a primary and secondary set that will be your mainstays throughout the game. The first one or two powers in each set are available and you choose one from each. As you gain experience levels further powers become available, letting you do more complex and/or powerful things within the theme of the set.
Appearance comes next. First you pick basic body type - male, female or "huge" male - and build, from short and athletic to tall and muscular. Then you design your costume. This is stuffed full of options, with very detailed customisation of features, patterns and colours. If you have a concept in mind you can spend a long time trying different things to get it just right. Alternatively you can do what I did for my second two characters and keep pressing the "random" button till you find something you like. You'll see some weirdness on the way, but because you can set a colour scheme to apply universally a lot of them do hang together. Then you can fine-tune - one of mine really appealed overall, but the eyepatch had to go! Unfortunately I neglected to spin the figure round before finishing, so he ended up with boot-fins on the back of the legs that I'd rather weren't there.

One of the central safe areas and meeting points, showing Shockbolt (front, yellow and blue) and several other weirdos. His costume was a completely random selection.
To finish off you name the character and have the option to give a description/summary/backstory that other players can see. Overall, once you've got to grips with how it works it is quite simple and you can always go back to earlier stages to try something different. It isn't, of course, totally freeform: if you want to do something that isn't covered by the available options, tough. This is particularly an issue with powers that would be covered by attributes like Strength or Agility in RPGs: you can only do those characters by finding vaguely relevant powers and then using Enhancements (see below) to beef up the relevant bits, and your choice of powers is restricted to two sets that go with your archetype. So if you have a strong concept - perhaps mimicking a comics character, though not too closely as they're sensitive about getting sued by comics companies - it's potluck as to whether you'll be able to make a good match.

Steppehowler takes a tumble - use more ice next time!
Gameplay
Here's what you do.
1. Random violence. Wander round the city beating up poor innocent street thugs and zombies. This is good for gaining experience and trying out powers.
2. Missions. You start with a contact person depending on your origin, and over time they refer you to other contacts. These offer you missions to undertake, like a patrol to take out a certain number of gang members or clearing out a hide-out, which draw you into the backstory of the game and take you to new parts of the city as your experience equips you to handle the challenges there.
3. Teams. Actually a way to undertake the other two: you join up with a group of other heroes (which gives certain extra benefits for communicating and helping each other out). This is a necessity for many missions - and really, as a key component of a multiplayer game, the experience can be a bit flat without it.
That's pretty much it. You can choose which bits of candy appeal to you most. It might be showing off as you pound baddies with your cool powers. It might be building your character up to be the ultimate in a certain area, or to fit a certain concept you have (for instance I decided Shockbolt would focus on being fast and accurate, alongside his electricity powers). Or it might be the social element. My first two characters went into zone called The Hollows recently. This is so hazardous that the police force has built a barricaded area with sandbags just inside the gate, which serves as the start point for expeditions into the zone. There's a tendency for heroes just to hang out here, check out each others' costumes and watch the world go by. Many indulge in the emote options of dancing and playing tunes on a boom box. Every so often a gang mounts a raid on the barricade, and anyone who feels like it goes out and stomps them. I think of it as the supers equivalent of a nightclub.
The interface is OK, though there's a lot going on if you have everything on display: powers, chat window, navigation, info about targeted character, etc. I have a degree of difficulty navigating around, using the keys for forward and back and the mouse with right-click held to change direction, which works in all directions and can lead to crazy disorientation. I put this down to my game skills rather than bad design, and I'm slowly getting more used to it.

The Black Spot (front) and team pick on some green guys
Progression
The most obvious effect of advancing in levels is that you get new missions and can explore more areas of the city without getting flattened. Your basic abilities to deal it out and soak it up increase.
Until you get to high levels you can choose a new power every other level. This will usually be one from your two main sets, and as you get higher new ones become available. From level 6 you also get the option of picking new "pool power" sets. There are probably about a dozen of these, working in the same way but with fewer picks per set and higher powers becoming available more slowly. This is where you find flight and superspeed (Flight starts off with "Hover", and actual flight takes a while).
Enhancements are the bit of character improvement you'll use most often, and they're somewhat confusing. I got the wrong end of the stick to start with and had to go to the CoH forums for an explanation - the quickstart booklet isn't clear at all. Each power comes with an enhancement slot, and every other level you get two more slots to add to whichever powers you want. Enhancements go in these slots and each improve one aspect of a power like range, accuracy, damage or the time it takes to recharge after you use it. You collect them for defeating some opponents and can also buy them from certain NPCs, using a currency called "influence" which you also gain for defeating opponents and saving citizens. If you get an enhancement you don't want you can sell it for influence. You have a tray with 10 slots for carrying them around in.
This is one of the major hooks of the game. You have to decide which aspects of a power your character should be particularly good at. Are they able to fire off attacks with great rapidity, or are they slower but doing greater damage when they hit? Each power has a number of properties that can be boosted: if you encase someone in ice, for instance, these include the accuracy of the effect hitting them in the first place, the damage from cold, the strength with which it immobilises them, the range you can hit them at, the cost in endurance (your energy pool, depleted by power use and replenishing gradually) or the recharge time (big powers can't be used often). Then you have to get hold of the right enhancements, by luck or trading, which in turn means gathering influence to buy what you're after. You can use more than one slot to boost the same thing - for instance, 3 slots of extra damage would be quite significant if that's where you want your abilities to lie.
And there's more, which is the complicated bit. Each enhancement bears a little number. Initially I thought this was its strength, and that I needed to go for the biggest numbers that came my way. Wrong! This is its level, and it only works if it's within 3 of the character's level. Enhancements higher than you are slightly more effective, those lower than you slightly less so. Because your level goes up and theirs doesn't, eventually you find that your old enhancements don't help you any more. Example: a starting character will equip slots with level 1 enhancements, but when they hit level 5 those will stop working so they'll have to go and buy level 5 ones to replace them. There is an option to combine enhancements, adding a new one of the same type on to an existing one to extend its life. Enhancements higher than your level + 3 are only of use to sell for influence or keep for later.
I'll mention Inspirations here too. These are one-time bonuses that you often get from defeating opponents. You burn them for a few seconds' boost to accuracy, damage or defence, or to recover some health or endurance (it's a pain to run out of power-juice in the middle of a fight). There's also one to wake you up again if you're defeated, rather than teleporting to hospital and having to travel back to your mission - very handy. You have a number of slots to carry these around, and at certain levels you get more slots, which is useful for keeping different options open. (With both enhancements and inspirations it's good to keep an eye on your slots, because if they're full you won't pick up the ones you might get from what you're about to do - sometimes it's worth deleting junk.) You can use influence to buy inspirations from your contacts.
Further up you get access to other goodies, like more powerful enhancements and a cape (which is a kind of badge of rank in Paragon City and must be earned).
Conclusion
If you like supers it's a good buy, as long as you're aware going in that it's basically a special-effect-laden slugfest - kind of like a first person shooter with more character customisation options and the social element added. Ultimately, if you want depth and lots of different options/modes of play, that's why we have "pencil and paper", human-moderated RPGs.
How supers is it? Probably about as close as you can get within the format. For manageability within the game there can obviously only be a certain number of powers and costumes implemented, and they've done a good job on these. You can't do property damage, which is a staple of the genre but would add a whole extra layer of stuff for the server to keep track of.
The other limitation comes from the players, not the game: people don't go around pretending to be superheroes. All the chat dialogue I've seen is from players, about the nuts and bolts of the game and getting tasks done rather than presenting a personality for their hero. Now a certain amount of this is necessary for practical purposes, but there are multiple channels of communication available including speech and thought bubbles for the local area and team chat across the whole game, so the possibilities for a bit of a performance are there and I've been making a few erratic attempts to present a public in-character face. There's also a lot of... well, silliness about - choices of character name and appearance, and the emote options like dancing and stuff. This is the way those people are having fun, which is great and fine and can be very entertaining, but kind of stops it feeling like emulating comics. (This might reduce when school starts again.) Again, it is what it is. I can see that a group of players could establish a sort of social contract and do performance CoH where they try to act out something more like a comics episode. But there are small things to do to improve the atmosphere - you could pick one or two emote actions as signatures for a character (e.g. with Steppehowler he sits in a cross-legged meditation pose at rest and roars when something annoys him). As a tool it's flexible enough for that.

