I've been a Verizon (on the America's choice network) customer for about 4 years now, and despite the odd customer service issue, it's going to stay that way. By far the best coverage, and call quality. Customer service is the usual game of roulette, but it can be lived with. I travel ALL over, and there are obviously the odd spot where coverage is less than perfect, but there don't seem to be many huge gaps.
My only gripe is that the are obsessed with having me under contract (currently I'm not), but they'll do anything to entice me onto another two year agreement. Even though I'm not going to buy a new handset (don't need one), and so they haven't got any upfront costs to recoup (the usual excuse for the contract).
So as long as you're prepared to commit to the first year, and then put up with people telling you that they can "save you money, if you'll just sign this shiny new two year agreement" after that. I'd say go for Verizon.
Recently looked at the Virgin service, which I really like (it's certainly the best no-contract service in the UK). Unfortunately they use the Sprint PCS network for coverage here, which is less than perfect.
Hopefully one day we'll all be able to focus on something more meaningful than coverage to select our networks of choice!