And don't think it's a Mac problem, either. It runs like a dog on high end Wintel boxes, too. As the previous poster said, try adjusting video settings - when I first ran, I noticed that it was using software rendering so I switched to Hardware acceleration - and that seemed to fix some speed problems.
Cool game - but it's buggy as sin.
Oh, and you can't rotate most buildings so don't pull your hair out trying to find how to do that, either!
-s'fit