I have to say you bring up a good point as there on sprints network, If you can byod, say a first gen EVO? I know for a fact ( one of my brother had one) the tethering ability was on lockdown and you needed to call sprint for a password after you paid the additional $20 hotspot fee! I believe its changed recently but who knows.
I currently have Walmart mobile, yup I jumped ship to test them out as of feb 1st, Hell I was on Tmobile to begin with so my coverage is exactly the same, reason I jumped? Got to use my stock Gingerberad G2X just pop SIM and GO. Instead of only 2GB of 4G highspeed data for $60 I get 5GB of 3G for $45 with unlimited T&T, I prefer quantity of high speed data, over top speed! I still tether and it works perfectly, BBR still says Im on Tmobile as my service provider on there home page. I receive a walmart discount as my other brother works for them...double bonus!