At one point their 4G was nice in my area, beat out my Home Internet at one point.
However it seems like the 4G WiMax service is in a state of decline. Can hardly get a 4G Signal at my house anymore, and anywhere else I go in Denver it's non-existent. For high speed I'm pretty much stuck with Wi-Fi. What I'm doing is moving to Boost Mobile, which though a Sprint Subsidiary is cheaper and will offer 4G LTE at the same time as Sprint when the LTE service here in Denver is ready. My rationale is a few things:
1) Boost Mobile is dirt cheap, for the price I'm paying now I'm willing to put up with near non-existent 4G
2) Don't need to worry about the lack of roaming, Sprint's voice/3G network is adequate for my needs, though I find myself somewhat envious of my friends on 4G LTE networks, when I compare phone bills I lose my envy real quick
3) If Sprint/Boost ever gets 4G LTE I'm Contract free and able to make the decision to get a hot new phone at the Sprint subsidy again (or another provider if I really get sick of Sprint/Boost and decide I need an awesome 4G network instead), no penalties involved