I'm actually an AT&T customer, but T-Mobile coverage has improved in a lot of the rural Midwest (at least it appears on the coverage map) but from what I can tell most of the improvements have been on Band 12. It seems like some phones aren't green-lighted for Band 12 service, so I'm just curious: if you had T-Mobile and pop your SIM in, does the DTEK60 appear to have T-Mobile US Band 12 support out of the box? If so, I may switch over once my new phone arrives and I get it all set up.
The area immediately around my home still doesn't have great T-Mobile coverage, but it seems like a lot of rural areas have been filled in.