When installing FC7t2 on a 12" Powerbook, the screen goes blank shortly after kernel starts to load. Adding video=ofonly seems to fix the problem. FC6 works fine here. This is mentioned on http://fedoraproject.org/wiki/QA/7/Test2TreeTesting but without a bug number, so I decided to file it.
Just checked with the newer rawhide version and it works again. Please discard.