The customer support is amazing. Though I don't trust their stores, still populated by some slimy sales people that try to slip on extras. Had one add Jump to my plan without asking, and my friend had a similar incident in another location. Phone customer service corrected the issue right away though and did followup with the store. Thankfully this year I can just go back to the Apple store to buy my 6s, they have full integration with T-Mobile's system now.

They were also good in helping to troubleshoot issues at a family members place. They were 20 miles from the tower, and would lose native T-Mobile signal in the summer. The phone would then find some obscure rural carrier to roam to that won't go above 50MB a month. The upgrade to band 12 is going to help, as it's going to push the signal just a little farther and should work summer or winter.