Huh, does it cost more to offer a Mac ver through steam? I have noticed a fair amount of indie games that have Mac ver's here don't have them on their Steam page.
Do you happen to have a a min Sys Req's for Mac? My processor is comparable to whats listed on the steam page for windows and i've got 12G of ram. But my GPU is a paired type (Geforce 320M). So driver support regarding some lighting/shading effects with open GL often comes up as an issue.