I get ok reception in my home city, but I was on vacation (within the US) last week and my biggest source of stress was how horrible AT&T was. One bar and Edge for a huge chunk of the southeast US. I could barely browse the internet at all, calls kept getting dropped. We had to stop at Starbucks a few times to get wifi to do things.
Even around here, there is no reception in random places. At work there is no reception. Even outside on the top floor of the parking garage, with no obstructions, 10 miles from downtown Boston, I have no reception. Most of the places you would take weekend trips to - northern NH, Maine, etc - no reception.
I have been miserable about AT&T since I switched from Verizon just for the iPhone. I can't wait until the day the phone is available on Verizon, I will be gone from AT&T so fast, I will probably pay an early cancellation fee and get a brand new phone just to escape. Even the most rabid Apple fanboys I know around here admit they will go to Verizon as soon as they can.
Looking forward to the day. To this day I have never used data features while talking on the phone.