Unfortunately I can't afford Maya complete at the moment, So I'm running the PLE version on my G4 400Mhz. As far as speed goes, it fast enough in use, goes to prove you don't need a 3000Mhz chip.
As fars as the unlimited version goes, I don't know. But I have read that alias|wavefront have been very impressed with the mac sales of Maya so its only a matter of time.
Does anyone know when the new PLE version 4.5 is out?