Pleasantly surprised here, for I wasn't expecting much out of it.
From the moment I started playing I was surprised about the fluidity of the game, in terms of how snappy the gameplay was. In addition, it is quite fast-paced and a lot of fun to play. Every single mission is a big set-piece, and you will love every mission for that reason.
Had no problems running this game at all, never once froze/destroyed/blew up/whatever my PS3 throughout the campaign. I have also played Zombies and Multiplayer and it hasn't done anything to my PS3.
Ignore the doomsayers and buy this game. You will love it.
Four stars because it doesn't do anything different in terms of gameplay - although single player is the best I have played in a COD game since COD4.