I'm with Sprint and on the best coast. Definitely not the greatest network, but I couldn't see myself being with anyone else given the price and unlimited data.
It's a little silly to compare them to Verizon, though. Verizon is the most expensive because they have the best network. That's what justifies Verizon's prices. People go with Verizon knowing that they are paying more for better service.
One of the complaints against AT&T recently is that they have "Verizon prices" while also having a terrible network. The best thing AT&T has going for them is they're GSM, which means they generally get a wider selection of phones. But people are leaving AT&T in droves. There are so many unlocked iPhone 4Ss on T-Mobile that T-Mobile has announced that they will have their network iPhone 4S-ready by holiday season, and T-Mobile doesn't even carry the iPhone 4S.