I game on my 2010 13" MBP. You really have to tweak performance settings, and it depends on the game. I assume the 2011 will do better.
But I don't play FPS or anything like that, that depend on higher performance.
I played through Sims 3, Starcraft 2 (campaign only, as multiplayer got really bad when lots of units were on screen), and Civ 4.