I just switched from Sprint to Verizon two months ago. I was with Sprint for 3-4 years. I was very satisfied with their service up to the point they adopted the iPhone. Once the iPhone was released, for me, the 3G service went down the tubes. The WiMax was nice for a while, but once they started messing with the towers to bring LTE, that went down the tubes as well. Once the iPhone came out, it felt like Sprint was a second hand network.
Being on Verizon has been nice. Everything is so much more reliable. It is a little bit of a premium, but I never have network issues, and where I am I average 20mb up and down.
I really hope Sprint gets it together, cause I thought their customer service was excellent. I never had a billing issue. Nor did I have problem they did not correct immediately.
My suggestion would be to really do some research on the data speeds and such in your area. There are some places that Sprint is very good in. Make sure where you live is one of those places or you will get very frustrated when you are trying to use up data at 56k speeds.