I'm on an rMBP, which is close in spec.. I also have a 2.6 and I'm assuming 2.6 cMBP also has 1 gb video ram. The one thing you don't have is the display, which lets me play games at non-native resolutions without losing quality. I usually play at 1650x1050 (or is it 1650x1028? can't remember)
I've played a LOT of games on mine. I bought it as a portable work computer that could also handle gaming on the go, and I have really got my money out of it! I've played:
Skyrim - medium-high settings, 45-60 FPS
Diablo 3 (on Mac) - medium settings, 60 FPS
FFXIV - "Laptop(high)" settings, 30-45 FPS
GW2 - 2880x1800, medium, 50+ FPS
It doesn't come close to what a similarly priced desktop could do, but it's a nice side feature. I'm very happy with my purchase almost a year later