I'm actually switching away from Verizon for my cell phone service this weekend precisely because of their role in destroying net neutrality. I expect T-Mobile to be slightly worse, or at least no better, in terms of service-per-dollar but at least my conscience will be clear. Who knows, maybe it'll even be better!
I actually switched from Verizon to T-Mo about two years ago, and while it isn't better than Verizon, it isn't substantially worse. If you live in a fairly well populated area (cities of over 5000 people or so), or along major roadways, I've never had any issues. The only time Verizon did much better than T-Mobile for me was driving through Western Colorado and Utah, where T-Mobile had no service, and Verizon barely had voice.
