In my experience, most people dogging on T-Mobile and riding the "they don't have coverage!!!" train haven't used them in the last six months with a modern device (read: supports Bands 12 [and 71 if in an area with it deployed]), rather are basing their opinions off of marketing from other carriers and what they read online from users with outdated devices that don't fully support the network...
I've been throughout 12 states + DC and had zero issues, except for West Virginia. But they've finally got that Band 71 spectrum to solve the coverage issue in areas like WV. I can use data to my heart's content on my frequent trips to Canada and not spend a dime on it. I even had free Wi-Fi on my last Delta flight that was subsidized by T-Mobile.
Perfect? Nah. Nobody is. At least I'm not spending $240 a month just to have a shiny red checkmark on my bill.