I used to have a 7 on T-Mobile. Reception was absolutely terrible. Service would drop out and I would have to throw my phone into airplane mode and back out to get reception again. Building penetration was nonexistent for LTE and very slow when "4g" was available. This is in the Dallas market. I experienced it from downtown to the mid cities to north Dallas. Never went to south Dallas, but doesn't sound any better.
Service is still terrible. A co-worker with an Android still has connection problems and continually is unable to make/receive calls when we're out and about.
I switched to Verizon after a couple months of missed calls, dropped calls and missed texts. It was really awful. Reception is much better now.