On the Steam forums, one user complaining of 'abysmal performance' was told Apple, Nvidia and ATI were all working with Valve to improve performance and things should improve as drivers are updated.
Lobsters: Anyone else getting about 1/3 of the performance that they normally would under Windows? I'm running a Mac Pro 2.93ghz 8-core machine with 16GB RAM. I have both the GeForce GTX 285 and a Radeon 4780 and neither of them get anywhere close to where I'm at under windows. Either card under OS X gets around 45 fps average under mild settings whereas under windows will net me ~150fps with completely maxed settings. I know there are some performance tuning options that guys use under windows to squeeze more performance out of the game. Does anyone have any tips for running under OS X?
Rbarris (VALVE): Performance is going to improve as drivers are updated. I would expect modest improvements in short term and larger ones in longer term. No, I can't put dates on them. We are making a lot of progress is identifying specific issues that need work inside the game and inside OpenGL and drivers. Apple, ATI and NVIDIA are all involved.
Check out the full thread here (via Engadget).