I have heard in the past that some US 3G USB modems already work, but "unofficially". If you have a 3G USB modem handy, try plugging it in and see what happens. Verizon in contrast would be "officially" supported.

Very early (March? April?) on when I asked about 3G support, enTourage told me that most carriers want/need a custom app to handle the connections, which is what this Verizon connection manager app sounds like. The "unofficial" others I guess must work at a more basic feature level.