Hi, I recently purchased a macbook pro 13" running OSX Lion. It serves me well for the most part, but occasionally games such as tf2 and killing floor will "hitch" for a half to quarter of a second. It occurs the most in the beginning of gameplay and gets progressively less as gameplay continues. I believed that it could be caused by the vram being too loaded so I tried lowering the textures and that definitely reduced the effect. However, it does not eradicate it entirely. My settings are maxed except aa. fps is a steady 30-40 but the hitching is unbearable.