20FPS if you keep the view distance and detail distance below 20%.
You really need a quad-core to get the most out of the game.
Got Mirrors Edge purchased as I've always wanted to try that. Tempted by GTA4 but don't want the sluggish bloated game, better off with the 360 version and it's DLC. Awaiting further price reductions on Batman now.
^in my experience the benchmark score is in no way indicative of the minimum framerate you get during actual game play. I'd say you should halve it as a rule of thumb. I clocked around 45(?)fps in the benchmark but the actual game would drop to mid20s in the more demanding places.
What are you using to measure framerate in game?
iv spent £27 already on games on the deals D: all <£7. how much you all spent ?