This article at The Mac Observer proves it. Also, as for your mouse choices, let me the first to say that my Microsoft Laser Mouse 6000 works perfectly fine with Mac OS X and all my other devices. It is one of the only mice I have found so far that does exactly what I need it to do. After I forgot mine on a plane last year I even ordered a brand new one.
If Ballmer instead had said that Apple's mice suck and that they are uncomfortable to use I would have fully agreed with him. They after all decided that a mouse shaped like a hockey puck would be a good idea. The Mighty Mouse is an interesting concept, but that is all it should ever have been. Sure the little ball in the middle is an excellent idea, and sometimes I miss it, it gets dirty fast and then it stops working. Sometimes it refuses to register right clicks (there is no physical button for right click, it is sensitive as to which finger is where), middle clicks would sometimes become just standard left clicks. Ugh, it was a mess.
Ballmer, your own company created mice work on the Mac, go out get a Mac and experience it for yourself, and stop spouting crap! Come back when you have some experience underneath your belt!