On a 1.83Ghz Core Duo with 2GBs of RAM and 128MB of VRAM, I'm seeing 50-60 frames per second in unpopulated areas with the graphics set to the defaults. If I ramp all the graphics up, I'm still seeing 40-45 frames per second in these areas. If I enter something like a battleground where there's lots of action going on, I'm seeing about 30-40 frames per second with the graphics set to the defaults and 18-28 frames per second with the graphics pushed to their limit. Keep in mind that 24 frames per second is a stop-motion animated film, and regular full motion video is normally 29.97 frames per second.
Overall, I'm ecstatic. Finally! A Mac gaming machine that actually plays games!
Dear Game Developers: the time to code for Mac is now!