For a bit of full disclosure: I've been (and still am) a T-Mobile customer since Jamie Lee Curtis was shilling for Voicestream on TV. For the majority of my time as a customer, I've been pretty satisfied with their service--especially for the price. There are a few dead spots that are severely aggravating--at my parent's house, inside my kids' schools, at the Panera Bread literally a three-minute walk from my office. I'm not a heavy data user, but the fact that it's difficult for me to live stream stuff while inside a building has been aggravating (and the ice rink's wifi is even worse).

I believe T-Mobile will let you do a "test drive" using their hotspot. I would definitely take advantage of that before you dive in.