I'm running it on an 867MHz G4 Power Mac QuickSilver, and it runs fine from what I can see. I haven't done a lot with it, but it seems very responsive. It does have 1.5GB of RAM, which can only help.
I don't know off the top of my head the differences in GPUs, but the iMacs probably is a bit more capable (GeForce 4 MX vs GeForce FX 5200 Ultra, with twice the VRAM).