Interesting extra:
I have a Belkin three-button USB mouse (connected to my iMac revB). I have no drivers of any sort loaded for this mouse, as I bought it once upon a time when playing with LinuxPPC. The right mouse button works great in OS X 10.1, but I noticed last night that it also works in MS Excel 98 running in Classic, giving me contextual menus.
When I boot into OS 9 directly, that is not the case. I have to use the control key to get contextual menus in Excel, so I assume that I get the additional functionality due to OS X/Classic. Nice bonus!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20011012093002861