Eh, well, Sprint here has the reputation for being utter shit. Maybe it's improved but I haven't known anyone that's used them in the past few years.
I drove from Georgia to Wisconsin and had my Tmob service the entire way. Yeah, it's a somewhat limited view, but as long as I can get where I want without losing service, I'm satisfied. The fact I'm paying $85 for unlimited everything (data/messaging/voice/etc) makes it even nicer. Their data tech rollouts are my only complaint...last one to get 3G, but fortunately I can get it even out in the country here. Most others aren't so lucky.
I worked for AT&T in the past and won't ever use their service :/ Have been with tmob since it was voicestream. Verizon I think does have the best coverage, but they are also the most expensive, you get what you pay for. Verizon has been known to make you pay to enable features that are built into the phone (gps, for example), their prices are highest, and you can't use data/voice at the same time (last I checked). My tmob coverage is just as good here, cheaper, they suck my dick since I've been with them so long, and in the rare occurrence that I need data/voice at the same time (out somewhere, have someone on the phone, deciding movie times, etc) it's an option.
I know some people satisfied with Corr or those other tiny cheap companies simply because they have coverage where they spend 99% of their year, and it's like $50 for unlimited everything.
Just have to look at what the best option is for your area...