I too read the Mac App Store requirement of OS X 10.6 and thought I would be able to play, but my 2006 MacBook Pro (2 GHz Intel Core Duo, 2 GB ram, X1600) is apparently nowhere near fast enough to play.
The game loads, but the menu interface is jerky, and the actual gameplay is just like dariusg described, and completely unplayable.
I was tempted to try the game on my Windows 7 partition via Bootcamp, but I don't feel like shelling out more money for another version that likely won't run.
I wish the Mac App Store listed real system requirements, instead of just assuming that nobody would keep using the same computer for five years.