I've tryed running PearPC on my ultra fast desktop and it's slow as a bug. Might be slow because PearPC only lets you use 64MB of ram to emulate. It can be changed in the config file but I didn't know the coding to change it. Also I think it emulated the RISC CPU at 233MHz.

Just wait for the Xbox 360, it will be running a RISC CPU setup. I bet some one will mod one to run Mac OS X.
To live is to let die