Both reviews on the apple website and pretty bad (2/5 stars), and they either talk about bugs and that the controls are clunky. Mind you there are only 2 reviews.
I can't say anything about the bugs, but the controls are the exact same as on a PC. Games like GTA have always been a bit awkward to play with mouse and keyboard, while much easier to play with a gamepad using, for example, a PS2 or XBOX. It is something to get used to, and not something to bash the game for, just because there are no good gamepads out for the Mac.