We've had Cingular/AT&T since day one. As far as customer service goes, I think they are #1. They have consistently gone out of their way to keep me as a customer. My dds have brand new4G Iphones and love them. The rest of us have pretty much basic (phone and text). I am happy with them.
That being said, when we went on vacation in upstate NY a couple of years ago, the only cellphone that worked was Verizon. I was impressed, but not enough to change providers.
They are iPhone 4's (as in 4th edition, not related to the type of network they use), not 4G iPhones. Although AT&T claims to have a 4G network, they really don't are are just using a loophole in the rules that set the 4G standard to pretend that their 3G network is better than it really is.