Nothing compares in my opinion and experience, but I do agree with others that AT&T is absolutely horrible. Every single interaction I have had with their customer support in their stores and on the phone has been a disappointment. They frequently mess up my bill and I have to call and spend time sorting it out. They have very customer-unfriendly policies, such as my wife and I not being able to share a family plan because she ported her old number over from another area code and you can’t have two area codes on one family plan.
They are extremely expensive, especially with extra things like text messaging.
I live in a suburb of Denver, CO with over a million people in it, with no mountains or skyscrapers blocking the signal and still only get a 3G signal maybe half the time. The rest o the time it’s EDGE only. I get dropped calls and delayed text messages, slow data transfer speeds, etc.
All that said, it’s still worth it to have the iPhone. It’s just that good.