I have the magic/mytouch android phone on Tmobile. Love android, and this holiday the market is gonna be flooded by android phones on every carrier. Apps store is very decent (pretty much every functional app on the iphone is in the android in some form or another).
The plan is cheaper than AT&T on Tmo but good reception is only possible in the city.
I see big things happening for android, as its being ported to netbooks and other devices.