I am on T-Mobile - but that is because my daughter is on T-Mobile and we can talk to each other for free - and talking to each other is mostly what we use our minutes. I have been completely satisfied with T-Mobile. I've been on it about 3 years now. At first there were some places where the signal was low, but that has improved greatly over the years.
I appreciate the information about U.S. Cellular - I don't care anything about the new fangled gadgets, I just want my phone to work and to be clear!
Good luck with your search for a new company.