Sprint has free first year unlimited data. Bring your own phone. I'm assuming that deal is still going on. Back in the day Virgin Mobile used Sprint. They both sucked horribly. No clue if that has changed.
In most places I've been, Sprint is perfectly useable, but not super-fast. I don't mean that as understatement: Sprint data is fast enough for things other than video streaming, but it'll never be the first to finish a download. There are areas where you won't have Sprint coverage, and they're largely the same as the places where T-Mobile is spotty, while Verizon and AT&T are likelier to work there. If you want to live your life assuming a constant uplink to the internet from your jeans pocket, you shouldn't use Sprint, but I suspect that a lot of people paying the premium for Verizon would do well to reconsider their options, since the dead zones for Sprint are where not that many people live.
FWIW, I've lived and traveled all over the east and west coasts, with a few drives between, in the last few years, while using Republic (Sprint) and Project Fi (TMo and Sprint).
I'm considering the deal for the ~$600 it would save my wife and me over the next year. Possible downsides are the headache of switching over and possible lifestyle creep...
