We've had Credo a little over two years and been pretty happy with it. After about one year, having started out with a couple of bottom-end Android phones, they let us upgrade to two E4GTs free on contract. They say Sprint's network isn't the best, but it has improved considerably around here (Palms, between Cheviot Hills and Culver City in L.A.). And in any case I'm not sure how much difference it makes in a large city anyway. We used to be with Verizon and there were plenty of dead spots around. Same thing with AT&T.
Credo advocates for progressive causes and solicits the customer's advocacy as well, so depending on your political leanings that could be an issue for you. But if that doesn't apply to you it's worth checking out.