AT&T may suck for you. No other carrier yet comes close where I live. Verizon had HORRIBLE service here. But I held out hope (as did many others) when they bought Alltel which was the closest to AT&T in coverage. But amazingly - nothing improved. That being said - I have not been to every corner of the USA with my AT&T phones. I do know that - so far- I have yet to find anywhere that I couldn't get reasonable service through AT&T that was any better served by Verizon or any other major carrier. Doesn't mean such places don't exist, just that I haven't found them yet.
One cool thing that AT&T has produced - an iPhone app that you can use if you find a dead spot or an area that calls drop (or any other issues, including data problems). It marks your GPS co-ordinates at the time of the trouble. When you get back into service, it will report that specific geographic location to AT&T.
It wasn’t only their network that I had problems with. When I called looking for solutions they out and out lied to me. Sold me stuff with the promise it would solve the problem, and it was usually worse.