Me too!
I was wondering if it was possible to downgrade through Time Machine. I haven't upgraded to 10.5 figuring everything seems to be working well on my recently purchased 12-Core, so why tempt the fates. I also use Pro Tools HD, which can be very picky about system software. It's also working fine. Any PT users out there that have upgraded with or without problems (oops, I suppose I should have said "issues."😉!)?