Just wanted to let everyone know that Palm Pre is very capable of feeding 3g to your carPC via USB, WIFI or bluetooth. (I can confirm wifi and USB personally) Get the Free homebrew app Mytether. Read about it and download it on precentral.net
http://www.precentral.net/homebrew-apps/my-tether
I used to use windows mobile to get 3g. I was scared when I upgraded to the Pre because there was no tethering solution. I'm glad this app poped up. It's very useful.