I live in NC, and I find my AT&T service to be spotty and I have plenty of dropped calls, mainly because of dead spots that I drive through or have around me.
I think part of my issue is that prior to AT&T (Which I started using before the iPhone was out) I had Verizon, and I was really spoiled with their network that works EVERYWHERE. Literally, everywhere. I could be out in the Appalachain mountains backpacking, and Verizon got perfect signal. AT&T drops as soon as I drive towards the mountains. Out on the coast of NC, along the Outer banks string of islands, I would take a ferry out to the farthest South inhabited Island, Ocracoke, out in the middle of the sound, nothing but Ocean all around, and Verizon had full service, perfect signal. AT&T drops halfway between my area and the coast.
So, I am happy with AT&T, and it works well enough, and I will admit that I believe Verizon has greater coverage in more areas, which annoys me from time to time, but overall, AT&T works fine for me.
But I have the best phone on the market (The iPhone) and it sure would be great to have it on what I believe to be the best network in my market.