The GSM only argument makes sense, however seeing as how Microsoft as far as I know was only responsible for the software, it would seem to me that a platform could have been just as readily available from HTC to work on a CDMA platform as the GSM one. However, it doesn't matter anyway, because this is likely to be just another epic failure. In my travels the main reason Windows mobile users keep windows mobile as opposed to moving over to other technologies is because the newer stuff abandons styluses. They are addicted to that way of doing things, and dont want to learn the touch screen keyboard and stuff. However, this appears to be so far removed from WinMO prior, that even their loyalists will likely re-examine other technologies since it is basically a late copy of other things in existence on all carriers. My opinion is Ballmer just hopes he can throw up a whole bunch of smoke and mirrors and herd the dumber users like sheep to their product.
Only time will tell I suppose.
Android FTW.