I just set my Storm up as a tethered modem. It was a very simple process using the VZAccess Manager. Download the software and follow the wizard.
The speed at my location when using the Storm as modem is 1.7meg down and .6 meg up. That's about 4 or 5 times faster than I was able to achieve with my Treo 600W as modem using pdanet at the same location.
I have an unlimited data plan with Verizon and modem usage is part of the deal.