Yes you can. I am currently running a mac mini and windows XP box through a KVM switch and it works fine. I have used the Logitech Cordless Desktop® LX 310 Laser keyboard+mouse combo as well as the Bluetooth Microsoft optical desktop elite (both USB).
You obviously lose some of the cool custom microsoft buttons on the Mac, but general use has been perfect. Funny thing is, the Microsoft keyboard/mouse works better with the MAC... go figure =P
Boece hit the nail on the head though. Just make sure you can return it, just in case.