I use a Mac as pretty much my only machine and I acutally use a Dell keyboard with it -- Apple, for some reason, swapped the position of the alt/windows (this would be Option /Apple keys on a Mac keyboard) and it's very annoying to use under Windows. Under Mac OS it's really easy to swap the meaning of these keys, so no matter which OS I boot into the key does the right thing when I hit it.

The only problem here is there is no (as far as I can tell) DVD eject button on a non-Apple keyboard, so I leave the regular Apple keyboard plugged in as well and off in an out-of-the way location for the once or twice a week I need to do that.