I don't really like the reputation idea. I just want to go online and play someone, without worrying about what they think of me. If I want to play with someone trustworty, I'll play with a friend, or just deal with it.
I've had a bad experiance with reputations before. In the game C&C Generals, you have a win/loss ratio (like alot of games) but (I could be wrong about this) nearest I could tell, that was the only option, everyone can see your win/losses even if it's not a ladder game. I tried multiplayer a couple of years after the game was out so mine was 0/0 and no one wanted to play with the 'noob' because it would damage their record, nearest I could tell, the only way to play 2v2 maps in my condition was to play nothing but 1v1 maps, get good, reset my record somehow, and start again with a clean slate.
Reputations might in theory, help against annoying players and general jackasses, but it would also mean that players are less likely to hand their controller over to their friends for a couple levels. It would damage their reputation. On the other hand, it may work like the new Battlefield 2 that isn't out yet, where they praise good players, but don't punish bad players, sorta like a win/loss ratio exept without the losses counted.