IMO Infinity Ward are by far the better developers but Treyarch have given it a good go and created a great game.
There's much less sniping and the maps to tend to have you running more than killing, it's completely different to MW2, the way I played in MW2 with Cold-Blooded and a Silencer, I've not even touched Ghost and Silencers on this game as there is no Stopping-Power Perk so it takes longer to kill everyone! Also the spawn points are sometime infuriating haha!
In all, it's a good game, nice to have a change from MW2 and Battlefield....it's all about Black Ops and Fifa 11 until the next game comes.....