AT&T is getting worse not better, it is by far the worst I have seen ever. I have Verizon for my work cell and it works everywhere and my iphone works in less than half those places. I love the iPhone but Apple should have opened it to other carriers that actually supply good coverage.
That's my experience with Verizon - Crapfest and AT&T with my iPhone is rock solid. I have a Verizon phone for work and it's horrible.