My only regret is that I had to remove my 3dfx video board first, but I'm sure drivers for that will come along soon. Otherwise, I haven't needed to switch back to OS9 for anything. All of my Classic apps work. And it's super-stable! I love being able to access the Unix command line (although for those that aren't into that, it's not something that you would ever need to do). Now I'm just on the prowl for cool OS X apps!