I really need to recommend that you should also take into consideration the type of
OS 'extras' that you will be receiving, as well as the
carrier.
Carriers:
ATT - You already know their coverage and whatnot. But also keep in mind that, at least I have heard, that their android phones are sub-par at best.
Sprint - Lowest rates on an unlimited 3G data plan. 2nd best data coverage in the nation, and 4G speeds (where available).
T-Mo - I know nothing about them, sorry.
Verizon - Possibly the highest rates? But the greatest coverage, and 4G coming soon (in the next couple years, I have heard).
Blah, I'm apparently not that knowledgeable in this area, but I think it's still worth considering. Others should chime in to help clarify
OS Extras
Samsung - The current lineup of Samsung 2.2 phones have something called "touchwiz" added to them. Check it out, I have heard good things.
HTC - Integrates "htc sense" with the Android operating system. I think this will lean the most towards the "rounded" and "flowing" interactions that your iPhone offered. Granted, it's nothing like IOS, but it has a more polished feel.
Motorola - I don't think they integrate anything with the Android OS. This option is going to be the most vanilla, rigid, no-bs version of any in the lot. It will be snappy and effective. But you can add a more 'rounded' third party UI overlay later if you like. Removing HTC Sense is MUCH more difficult.
OK, I now have laid out just how ignorant I am to everything new other than the Verizon/Sprint and Motorolas/HTCs. So take everything else with a grain of salt