Ah anyway, I use an iMac 27" with a Mobility Radeon 4850 at 1GB DDR5, Intel Core i7 quad 2.8GHz and 8GB RAM DDR3.
In the Bootcamp is installed a Win7 64bit, and I use MacFan to speed up fans in bootcamp.
Best game settings that I enjoy: 1920x1080, graphical 9 and background 5
DoF and AO off, texture highest and filtering standard.

Most common issues: Rain and bushes makes me stutter, and I also stutter when someone near teleports, sometimes.