Bob,
Here's my experience, using 3G devices at home. I had an ATT HTC Tilt phone, and got the "tethering" option to use for my Internet connection. (I wanted to see how it would work.) For the most part, it worked fine. However, I had to find just the right spot to lay the phone to get a 3G signal. I was getting around 900kb download speeds with the 3G connection - sweet! If the connection dropped to "E", it was like a dial-up connection (25kb - zzzzzzzz). I switched to a free iPhone (a friend upgraded to the 4, and gave me his old 3G). With it, I could only get a 3G connection around 30% of the time. Placing the iPhone in the same sweet spot as the HTC didn't matter. I switched back to a high-speed connection, since it was the same price as the tethering option.
I would expect the USB modem to work basically the same - having "sweet spots" for the laptop. During my testing, I was able to get my email anywhere in the house, no problems at all. I'm not sure, but I'd say you could signup for the Verizon data plan, try it, and then cancel within 30 days if it's not usable.
My 2 cents. ;o)