Good guitar tablature programs?

So i'm about to get an iMac, and something just dawned on me, i wont be able to use the tab software from my pc. A cursory search through google found several PPC programs, but no universals. I'm sure there are some, I'm just not looking in the right place. Anyone use one or have any recommendations or advice? I was also wondering if similar functionality is bulit into garageband? I suppose if worst came to worst i could boot up windows in parallels everytime i wanted to do something, but that's no fun.

Thanks in advance