I'm on a 2 Ghz Mac Pro with Snow Leopard. To me it is sluggish and awkward. iTunes 8 on Leopard was much better. I'm sorry Steve Jobs. But I don't see things getting better here. I see them getting bloated. At this point I could not say "It just works". So it's back to Leopard and iTunes 8. Fortunately I kept my primary hard drive that way and have only tried Snow Leopard and iTunes 9 on my secondary drive.