If you've tried Lion, the newest version of OS X, you've probably noticed that the scroll motion is opposite everything you've trained yourself to do. If you're like me, you might have found this pretty disorienting.
I stuck with it for a few hours, trying to undo muscle memory, and then switched back. However, my brain was already half in transition, so I decided to press forward. The paradigm is now more focused on the page, and less on the scrollbars, and I think it's going to end up being the right decision.
Unfortunately, I still have to use some Macs running Snow Leopard. If you've flipped like I have, you might find this tool useful:
This is a simple program to do the flip on earlier versions of OS X, and just might make your life a little bit easier. It did mine.