I just wanted to throw this out there, since I was absolutely jumping out of my skin when I found out....

You can now view/edit/play/whatever Powertabs on MAC! (and prolly linux too)
Also, even though GuitarPro released a mac version (total shit), there are a few free GP readers/players out there too...

Found via Sourceforge.net: TabView, DGuitar Pro and TuxGuitar
See my blog for a bit more info

Or you can just go straight to the source:
http://freshmeat.net/projects/tabview/
http://dguitar.sourceforge.net/
https://sourceforge.net/projects/tuxguitar/