DvDongle and Wireless Broadband Issues.
On several occasions I have used the DVDongle from Virginia to the Alabama Gulf Coast while using a Verizon Air Card. I had no problems whatsoever. That includes extensive time in the Smoky Mountains and on the Blue Ridge Parkway .
I always used a Verizon card because that was what was available to borrow from work. Nationally, we are about 80% Verizon, 15% AT&T, and 5% Sprint. Those numbers represent contract preference, not user or network availability preference. As an IT support person I get way more complaints about the AT&T service than the other 2 combined, but it is almost always due to service availability, not the quality (or speed) of the service. As for quality of service, they all seem to be about equal as far as I am concerned.