I've had AT&T since the day the 3Gs launched and both it and the 4s worked perfectly, other Android phones, as well. The iPhone 5 has been a data connection nightmare. I've already had Apple replace it once - it dropped right while the person was working on it, spoken to AT&T on the phone several times, but it loses data all over town.
From what i can tell, if I get in a marginal connection area, the data drops and never reconnects. This is most apparent when I'm in a call. I use a headset when i talk so I always see the screen, and see there is no data connection at all. Sometimes when i hang up the data returns or says Edge for many many hours. Sometimes it never returns and I have to restart the phone. Sometimes even that doesn't help.
I've tried every combination of settings, nothing helps.
Neither Apple nor AT&T claimed to have ever heard of the problem.
I'm going to trade my mom for her 4s, she doesn't use data 😉