Looking to get the TB when it releases in August 2012 (just kidding)...
Question: I thought I had seen that although the tethering/hot spot is a feature on the phone, there is an extra cost over and above the unlimited data charge - and that it was $20 extra per month.
So... assuming the unlimited data stays the same... it would be:
$29.99 - unlim data
$20.00 - tethering/hot spot
<gulp> the wife is going to nix that!