wmwifirouter sucks batteries like none other due to the fact that you have to transmit in the cell phone frequency as well as the wifi frequency. This works fine and dandy when you have an AC outlet handy, but if you are on the baseball field with no power, I'd imagine you'd have better luck connecting via USB to save power.
PDAnet works great for this purpose, but it is commercial software. From what I understand there is also a free way to hack the registry to prevent Sprint from detecting tethering.
http://forum.ppcgeeks.com/showthread...+ICS+tethering
I trust PDAnet more as it completely bybasses the ICS which decreases the chances of Sprint picking up on my tethering.