All carriers ultimately suck.
That said, aside of their delays with GDR2 I am happy with AT&T. They're a little more expensive, but their customer support has always been top-notch for me. Plus, AT&T is the only network that has consistent quality service both at my home and at my office.
I was on Verizon for a while in my pre-smartphone days. Their coverage was good but their customer support sucked all the things. Which is why I switched to AT&T... well, that and the iPhone, heh.
Anyway, your mileage may vary and all that.