We have T-Mobile and have for quite some time. We are pleased with the service and price, we pay a total of around $123/month for 4 lines. We have a plan where we buy our own phone, we don't finance any of that stuff.
We were notified the other day we are getting a free upgrade to get unlimited data on all of our lines instead of what used to be data stash. We've not had an issue with data before as iHeart radio and a few other apps did not count against your data anyway.
As far as service, in previous years we just knew going to my family (smaller town in Western Iowa) or my wife's family (small town in Eastern Iowa) there would be service issues. Going to Western Iowa we still have a few dead spots between Des Moines and Denison but we have service now in both of the actual towns we go to. Eastern Iowa we have no dead spots on the way now.
Overall I am happy with the price and service, can't ask for much else IMO.