Let me be a complete and total fanboi here - City of Heroes is pretty damn good. I've only been playing for two days but the game has the best low level game I've ever experienced in any MMORPG.
There is no down time and you get to do cool stuff right away. You don't have to go wack rats out in a field for ten or twenty levels before you get to wack rat-a-sauraus'in a different field for twenty more levels.
There is no crafting.
Everyone looks different and seems to have different powers.
Combat is fast, furious and team based.
If you don't like joining a group, this isn't the game for you. I've solo'd some and it's dull by comparison. That being said, it's easy to find a group and there are in-game tools that make it even easier.
Lots of eye-candy.
There is no camping. All the dungeons and missions are "instanced" content so you aren't fighting others for the spawn or loot.
It seems to be a pretty big world and I've spent a lot of time running but I just hit level 6 and started flying so travel should speed up.
It's a lot of fun. I pre-ordered it this morning. There doesn't seem to be many bugs and I've experienced little or no lag with 30 or 40 player characters on my screen at the same time.
I have no idea if the high level and end games are any good but I'm pretty sure I can get at least a month of entertainment out of it. It will be interesting to see how the high end game works since you can do so much right out of the box. If you enjoy MMORPGs and you're looking for somehting new, pick this game up!