I've had it since Tuesday. Haven't played any of the campaign other than the very first mission and have spent all my time in multiplayer.
Being a Treyarch game, it definitely feels.... different than what I would consider the "core" CoD games from Infinity Ward. It's got a lot of good ideas that are improvements over IW's Modern Warfare 2, but the online mode is suffering from some awful hit detection issues, and overall visuals feel mushy and bland (mostly in the texturing). I absolutely hated Treyarch's CoD3 and besides the beta, I didn't even waste my time with World at War. I hear from others though that a lot of issues and complaints with the engine from WaW have carried over here. TBH, I'd almost rather have the cheaters and glitchers of MW2 over the garbage lag and hit detection errors of Black Ops. I'll give it that it's the best game Treyarch has made... which means it's still not as good as IW's old CoD4:MW...