We own a brick and mortar business. Thanks to great employees and our ability to leverage technology, we're able to travel quite a lot.
In order to stay connected to our business we've always traveled with phones on every network. We can sniff out somebody's signal pretty much no matter where we are.
My main line is T-Mobile and I switch to other networks, as needed, on our trips.
We just spent the last few days driving cross country (something we do 3-4 times per year) and, for the first time ever, I didn't have to use any phone except my primary T-Mobile line.
I only lost signal for a few minutes at a time, and it was only a few times during the entire trip. It would not be an exaggeration to say that I had data coverage 99.9% of the time.
A friend of mine has a farm in rural Georgia and they've always only been able to get Verizon signal. I recently noticed that my T-Mobile phone not only works there, now, but I get 4 bars of coverage. I didn't even have to turn on my TracFone/Verizon phone, like I usually do.
Anyway, FWIW, T-Mobile seems to be well on its way to be an "only one phone required" network for a lot of people.