No one has mentioned HTC....wonder why?
I'm using an O2 Xda Orbit 2 and love it. Sure, this is UK's O2 wireless rebrand of the HTC Touch Cruise, but it's a "smartphone", GSM quadband, works in the U.S. on AT&T's 3g network, has GPS capability, runs on Windows Mobile OS and does not have a full keyboard but keeps a larger (touch) screen with a simple keypad and navigation wheel thingy.
HTC has some very cool phones, most are marketed overseas and some don't have the 3g capability in the U.S. unless they are picked up by our U.S. carriers and given a different name. Only ones I found (for AT&T) was the Touch Diamond, Touch Pro and Touch Cruise. Anyways, I'd say keep on eye on HTC and maybe see what they have or will have....depending on needs.
They arent bad phones I am sure since G1 is made by htc.
I had a treo that used windows mobile and I hate that OS. maybe was my dumb luck. I love palms OS and would like to try others.. Why i can I not be one of those people that test out gadgets for a living