It runs surprisingly well on my aging Power Mac G4 dual-450 with an original Radeon. I run it at 1024x768/medium and tend to get 15-30 FPS, which is fine for a game where no twitch reactions are necessary. I think it's dual processor aware.
Obviously it runs better on my gaming pc (P4-3.06/R9700Pro), but the Mac version is without a doubt MUCH MUCH more optimized.