As jerked around as I feel by Sprint in other areas, I do appreciate that they've let me exit my contract with a minimum of harrassment. I've heard some horror stories about people from Verizon and Ma Bell thinking they could get away with not renewing months in advance without being robocalled to shit.
Having worked for Sprint, here's some insight on the topic of Sprint in general;
Most of Sprint's service issues are entirely related to their network. They're a CDMA carrier like Verizon is, and CDMA has the disadvantage of being naturally shitty for Voice. Verizon gets around it by having an assload of towers, everywhere, but CDMA data is a lot more stable and consistent because of the nature of the format. Data has to piggyback on GSM, which is why they were stuck with 2g until Sprint and Verizon were half-way to 4g data. Sprint has a preferred roaming agreement, though, so if you think Verizon would provide better service, throw your phone into roam only for a few days and see how you like your voice service. There's only one other major CDMA carrier in the US, Verizon, and a few minor ones based on the city you live in - MetroPCS and Cricket probably being the notable ones. All the other CDMA carriers are just wholly owned subsidiaries of Sprint or Verizon.
re: Contracts, Sprint's been sued a few times over contract renewal and they mostly hate their customers anyway. Sprint's repeatedly gotten into the spotlight for dropping huge numbers of customers from their service for abusing service credits or roaming too much, so somebody not renewing their contract (esp. if you've called and complained a few times) is not really a big deal to them. Sprint is a budget carrier by any other name - their plans are much cheaper than their competitors and they offer "local plans" for "urban areas" that are insanely cheap for how feature heavy they are. They will pretty much always have a niche as the best of the budget carriers, so they don't have to worry about retaining 150-200 dollar/mo contracts like Verizon and AT&T do.
Also stay away from T-Mobile, they got really shitty after their merger with AT&T was blocked by the FCC and they have not been upgrading their network. My contract can't fucking end soon enough.
Sprint does have shit poor coverage in my state but other than that working with their internal reps when I sold cellphones for them soured me to the entire company. They were the type of company who I'd call them to do an activation for a new customer and they'd put me on hold for an hour.
As a former internal rep, I...
This is actually a problem with every cellular carrier. They spend as little money as possible on hiring employees to maximize profits, and if it's a busy period - say, 6pm on a friday - you can look at an hour+ hold time. If you actually get on the line with them, most sprint reps wash out after 90 days, so chances are statistically high that you're talking to a new employee. Sprint's billing system is incredibly difficult to navigate and activation is a multi step, pain in the ass process. It's even worse if they're number porting. And if you worked for a reseller, they can also hit problems with used phones - fucking huge ones. CDMA doesn't have sim cards as you probably know, so if an MSID is in use it can be an incredible pain in the ass to free up a phone for a new user.