I have a DP1000 Gf4ti rig and without changing anything, saw my fps rate in Q3 1.32 drop from 170 to 83.
I run the game at 1024x768 high quality.
That was really, like, a bummer.
This morning I trashed my config (in the game directory AND in the users/you/application support/q3/baseq3 directories) and let quake build a new one for me.
I then restored my graphics settings and voila, most of my fps returned. Demo four now runs at 150 fps, so I'm only down 20 fps now, which I can live with.
I wish Nvidia would release mac driver updates with the frequency they release windows ones. That would be sweet.