I switched to Mint ($15/month plan) a couple of years ago and don't regret it (it's on T Mobile's network).
So depends on your needs, but personally I live in an urban area where any carrier will get me decent everyday service, and for outdoor stuff, I have a PLB if I need to get help, beyond that, if I'm outdoors I'm doing stuff and I'm not spending time on my phone anyway.
So is it the best network? Probably not, but it gets the job done. For my personal situation, it's great value, no point in spending 5x more for a marginally better network with another carrier.