i'm on 7.3 here, on a mac pro with 10.5.1.
haven't done any full blown testing, but it appears to work ok (well, if you call the psyco colours on 10bit YUV codecs ok, but that's been an old issue with intel macs)
if it's a critical machine, make a backup clone of the current system drive to an external disk, so if things go weird it takes you three clicks to go back.
++ chris