T-Mobile but I plan to get a sim-free from expansys...
Also really don't want a pocket pc phone - from my experience from my hp ipaq the battery is not good and the bigger the display the bigger the battery drain. Also not a lover of stylus use.
Get either a qtek8500 (Imate smartflip) That has windows mobile smartphone, not Pocketpc, or maybe one of the Nokia Eseries devices, like the E70, or e60 they can also sync with Exchange
Strange no one has mentioned the HTC MTeoR 3G Smartphone which I thought would of been top of the list? Is there something not good with this phone? (which I am concerned is basically the same as the imate sp5m which I have now - or does this have much better specs?).
Also the E range of nokia have qwerty keys that drive me mad. I like the look of the N73 or the N80 but can't find out what software I can get for it to make it sync with exchange and offer push email?
Not all of the Nokia E series has qwerty, Specifically the E60, E50, they are standard candybar style phones. and the E65 is a slider with a numeric keypad