T-Mobile is about the same as Sprint and AT&T, and all are sub-par to Verizon. But what's nice about T-Mobile is that you get unlimited data, whereas with Verizon, you'd better cash in your fleet of 777s to afford your bill.
Sheesh.
http://consumerist.com/2013/06/07/t-mobile-has-a-30-unlimite...
http://www.walmart.com/ip/T-Mobile-SIM-Kit/24099996
http://www.walmart.com/ip/Tmobile-30-Wireless-Airtime-Card/1...
Some have good reasons why (mainly coverage, tho TMO is getting better), others are forced to question their contract policy.
Right now I'm paying monthly at TMO what I paid on Verizon+AT&T for me and my wife - except I now get 3 other smartphones on the plan for the same price, all with their own 500M data pool.
Once the new phones are paid off (i.e. equipment loan), I'll be paying just a bit over what I did for just one of my lines for all five lines I'm paying today. And no other carrier in the US has HD Voice.