Kevin and I are still happily consuming our <5GB per month of Verizon EVDO goodness and I also have an AT&T 3G data plan with my iPhone.  One of the most daunting factors affecting those who want a mobile broadband plan is certainly the cost and an article on GigaOM may be of interest.  Stacey Higginbotham has an overview of all carriers offering 3G plans in North America and gives us the scoop on the cost involved to play with each of them.  Of course, coverage in your area of interest is another big factor that must be taken into consideration when trying to decide on a carrier.