A letdown of epic proportions!
First the good. Graphics are decent, the cell shading gives everything a crisp, comic book like, look. Environments are decently done. The Character Builder provides a large amount of customization.
The bad, and there's plenty of it. There's an enormous lack of content. Currently, there are only 5 zones total. Each is large, but for the most part is just open space. Some will tell you there's a lack of quest causing you to grind to level up; I never found this to be the case, but I sometimes PvP'ed through whole levels. There is, however, an extreme lack of end game content. This is exacerbated by the fact that this is an extremely easy game. You can level all the way to the max level of 40 without ever grouping if you like. Many "recommended 5 man" quests can be completed solo with a bit of patients. This left me more with a feeling of being a super powered bully, rather than a super hero. To truly find a challenge in this game, you have to look to PvP. PvP, however, is plagued with its own set of problems, and they're grand indeed. There is little restriction to what powers you can actually acquire in CO. You are only required to have a certain amount of non-energy building powers in order to gain access to powers outside your chosen spec. There's also a big problem with balancing. This means you get a large portion of the population all running around with the same or very similar powers. You can craft your character to have the most overpowered damaging abilities while at the same time grabbing the strongest healing abilities. Genuine uniqueness in a character build is often rewarded with quick deaths in PvP arenas, quickly turning newer players away from this aspect of the game. So you see the same people with the same powers over and over again. Couple this with only 5 PvP arenas, leaves the whole PvP experience feeling weak at best.
This game really isn't worth buying at the moment. It's possible that all these problems could be remedied in the months to come, but as with most MMO's nowadays, if you don't grab onto and hold a large customer core from launch, it's inevitable for that game to fail; ie AoC, Warhammer, etc.