If you are on T-Mo the MDA is the flagship PDA. It's a sibling of the i-Mate KJAM. Treos are pretty good too, though you would have to get one unlocked. The GSM Treo 650 is available now, and the GSM Treo 700 is (supposed to be) coming soon. I'm not sure if they are going to bring out the palm or the windows mobile version first though.
If you like the blackberry design, the Nokia E91 looks pretty sweet. The Nokia Communicator is another smartphone they offer. Then there's the Blackberry 8700g for T-Mobile if you like an actual blackberry. Lotsa choices here. =p
Personally I'll take one with WiFi since I have access to free hotspots.
http://www.phonescoop.com/phones/compare.php?id%5B%5D=834&id%5B%5D=607&id%5B%5D=638&id%5B%5D=781&id%5B%5D=832