from a lot of the reviews i read, many people suggest actually just getting the Windows version and running it in Boot Camp instead. not only does the Mac version not even work with a Mini or MacBook, but graphics and performance are sub-par compared with the Windows and console versions. i can't confirm this since i don't have it, but that's just what i've been reading. i'm sure being a Cider port is where the blame lies.
and looking at the very hefty system requirements for Guitar Hero III, i'm guessing it'll be a similar situation