I just got a 3 button mouse (2 button and scroll) for OS X, and it's absolutely a sublime experience. I have no idea why Apple doesn't make this the standard on their machines.
I would highly recommend getting one. It's wonderful with Jaguar.
Me neither, OSX already has those context menus and it's much easier to right-click then control-click or whatever.
I could live with the one button on my iBook, but I can be a lot more productve with at least another button.