only time I have an issue with AT&T (specifically iPhone), is when I'm in a really crowded area. Example - SugarBowl, RoseBowl, jerryworld, Kyle Field, DR Stadium, and BDS. never fails - phone/sms no worky, while others with blackberries on AT&T work - I think Apple has let AT&T take the heat.
granted, AT&T in Bama sucks...