Over the past 12 years I’ve been a customer of Sprint, T-Mobile and Cingular/AT&T for wireless service in the US, and from this, I have a simple view of what you get from each one. During that time I’ve lived in the San Francisco Bay Area and traveled pretty extensively in cities on both coasts and in the rural Pacific Northwest, so that’s what my coverage comments will be based on.
(I’ve never been a Verizon customer, but it’s widely agreed that their service is both good and expensive; it’s easy to verify their prices are on the high end, and friends and family who use their service like the quality, so I’ll repeat that viewpoint).
Summary: Sprint and T-Mobile are cheap; AT&T and Verizon are expensive; Sprint and Verizon have good coverage; AT&T and T-Mobile have weak coverage; that means Sprint is cheap and good, Verizon is expensive and good, T-Mobile is cheap and weak, and AT&T is expensive and weak.
Sprint, in 7 years of use, has always been the cheapest for the level of service I get, and it’s always worked fine for me. Sure, there are rural areas where they don’t have coverage, but in my experience their coverage is wider than T-Mobile and equal to AT&T, and anywhere they don’t have coverage, you can roam for free on Verizon. Voice quality has been good; usually with even 1 bar of signal strength conversations work fine. Sprint often gets dismissed as having bad customer service, but that hasn’t been my experience; also, in my view, the best customer service is the one you have to deal with the least, and I didn’t often have a need to call them.
T-Mobile was priced about the same as Sprint, but their coverage was notably worse, both in the rural Pacific Northwest, and in urban San Francisco. I had no real complaints in 2 years as a T-Mobile customer other than lack of signal coverage in areas that mattered to me; that’s when I jumped ship to Cingular, since I could bring along my existing GSM phone.
AT&T worked OK (better than T-Mobile, no better than Sprint) with the older phone I brought over from T-Mobile, until I got an iPhone in 2007. That started 2 years of frustration, ultimately leading me to decide that the GSM networks in the US haven’t kept up in terms of network quality, and bringing me back to Sprint. In 2 years of iPhone use, I had daily experiences with dropped calls, incoming calls that went straight to voicemail, and garbled voice during calls that went through, all of this often with the phone reporting 4 or 5 bars of signal strength. Voice calls weren’t the only problem; often I’d take my phone out to look up a map or kill a few minutes reading mail or the web, and be unable to do so, so I take issue with the general assumption that the iPhone is a bad phone but great for everything else and so great for modern people who don’t care about voice calls — those people probably expect reliable wireless data, and aren’t getting it. One observation I made during this time was that while every carrier’s coverage has dead spots (they even have maps of this!), dead spots in space are pretty easy to route around — you know where they are, and you can avoid them. But AT&T’s network is the only one I’ve seen where the signal quality varies hugely in time as well, that is, where you could have perfect signal quality at one time, and 5 minutes later in the same spot, no usable signal at all. For me, signal quality that varies in time is far more frustrating than signal quality that varies in space.
(There’s plenty of agreement on AT&T’s dismal service quality, especially in cities such as New York and San Francisco, and plenty of speculation on why — maybe it’s the iPhone itself that’s buggy, maybe there are simply too many users on the network — I just know that the 2 different iPhones I had were not reliable for either voice or data use in the US, and they both worked a lot better overseas on other networks once I unlocked them.)
So of the 3 networks I’ve tried, only Sprint was cheap and good; that for me is a compelling combination and brought me back to them.