Over the holiday break I had the chance to really put 3G networks and mobile connectivity to the test while en-route driving between Illinois and Florida.  I was working with my MacBook Pro connected via WiFi to a CradlePoint WiPipe access point that had my Sprint broadband USB adapter in place.  The WiPipe did a great job keeping a good connection up and running (it seemed to be much better about forcing a reconnect when things got really slow than the Sprint drivers on the MacBook Pro with the USB dongle plugged in directly).