Maplassie
AK47 Pew Pew
The game utilizes the in-house IW 4.0 game engine, which is claimed to be a generation beyond the capabilities of the engine used in Call of Duty 4: Modern Warfare
Wich leads me to believe. If you can play WAW (which is more demanding on your rig than 4) Everything on MAX, lekker High Rez, then you wont have trouble with MW2 on medium settings.
Bear in mind alot of new physics objects and destructables have been incorporated. Also the game uses advanced new Ai, and MUCH MUCH bigger levels, as they require Texture streaming, a first for a COD franchise game.