MP is fun but not replacing cod4 as my favorite MP game (yet).
Free for all - seems like the cars disappear and the city becomes a ghost town after a little while in game. This causes all the players to leave.
Cops and Robbers - cool idea but the Boss dies too quickly before restarting the round. I kinda wish that the Boss just respawned and the game kept track of kills or something.
Deathmatch - fun, but ends up with people just running around pistoling eachother. I wish there was a little more car play instead of foot play. Plus, people respawn very closely together.
Minor gripes, I'm sure I'll like it more as I play it.