One simple reason I switched back to old-style scrolling: I also use Windows, and would definitely have issues going back and forth with the different scrolling styles.
I've been using Mac OS since 1985. Not really interested in flipping all the scroll bars over. I'm sure I'll eventually be forced to upgrade but I'm in no hurry.
I use Windows at work and Lion at home with the new scrolling. Have not run into any issues or annoyances yet, not sure what the big fuss is all about.