If you ever get a charge for it just argue that it should fall under the "Premium Data" tax they're charging you for using a smartphone.
As far as data usage, how fast is a phone connection by WT? I have used it when I had a Pre, and it was adequate to work with on my laptop doing office paperwork, but not enough to stream good video or music at the same time.
Just a note. I used my wireless tether to stream my live NBA games via NBA league pass and Use my PS3 online to play COD Black Ops with voice chat without any problems.
I'm sure it helps that I have 4g in my area![]()