I see a lot of negativity on this thread and I think it's a little silly. Allowing people to use their existing keyboards and mice is just a cost-cutting move because a lot of people have them from an old PC. Better that than a $599 base system.
As the owner of a $5,000 plus Mac system (PowerMac G5, Cinema HD Display, 3.5gb RAM, etc, etc), I think this is an excellent thing because it brings more people to the platform and encourages more development. That helps me at the high end as well as those on the low end with the new cheap machines. I'll probably even buy one or two myself for home control and similar applications.
Connecting a 2-button mouse to it will make the second button behave in a similar way to Windows - it will be like Control-clicking the item, which is the same as right-click on a PC.
In other words, it will work just fine out of the box.
Hope that helps.
D
Sure, as long as the old keyboard and mouse are USB. Granted, I haven't bought a turnkey PC in quite a while (I build my own) but, how long have (bargain) PCs been coming with USB mouse and keyboard?
Also, if PC converts are hoping to use their existing PC monitors, do Macs now have standard 15-pin VGA ports? They didn't back in 1995, the last time I owned one.