[fryke]

Apple was asked for two and three button mouses for years now, and they always stated the same thing (no assumptions or rumours needed here):

'The Macintosh can be used with one mouse button. We want this to be the easiest experience for new users.'

Or something along these lines. Of course power users always wanted more buttons, but then again they always had the chance of doing so. Kensington trackballs have been around for Mac forever now, and so have Logitech mouses. As long as Apple does a context sensitive menu with ctrl-mouseclick, this is no problem at all, because you can program your mouse to use that. And in Mac OS X the right mouse button is automatically set to do just that without any third party software.

However some betas of Carbon applications (namely Illustrator, InDesign) have problems with it. They give you a menu on ctrl-clicking alright, but they don't on right mouseclick. Guess that'll be fixed until release, though.