I am perfectly fine with AT&T.
Why should anyone change, when you can't use the phone and data at the same time? So if one gets a call, and want to find a location on Google map, one has to hang up first. That sucks the fun out of iPhone. Not worth it!
I use my data more than phone. I am reading my mails when phone comes in, and I can handle both on AT&T. I can use phone and text at the same time. Internet search and phone, etc.
I am staying with AT&T. No, I am not going to switch, even if Verizon is giving iPhone for free!
