I don't even care about speed once it is in the two-digit Megabits. I just care about reliability. And that is where it ended with Sprint in my area. I could pop 20Mbs without much problem at certain times on LTE, but then 5 min later have no connection or the network would just freeze or there would be zero upload speed for no reason. 3G was still a ghetto wasteland anywhere there was population (42 Kbs to 200 Kbs typical during the day, even months after Vision upgrades). Meanwhile, my text messages wouldn't go through or would repeat endlessly. And I dealt with that for over a year, so it wasn't just growing pains from "Vision" installation.
Sprint had/has some serious network issues in many areas (apparently my 1.7 million person area was one of them). I believe some of it is technical, some of it is being grossly overloaded/oversold, and the rest is the "unlimited" data mentality allowing people to just do stupid stuff all the time, draining what little network is left. I hope they get their act together, because competition is a good thing for everyone. But after 15 years, I really had no choice but to leave them. When I moved to T-Mobile, all my network and texting problems instantly disappeared, permanently (so far, anyway).