I ordered my iPad early and opted for the WiFi only version because I didn't think I would need the 3G connectivity. If you have been holding out for the 3G version, you will be able to use the thing as a massive GPS device in your car.
Copilot Live HD for the iPad will be coming to the App Store just as the iPad 3G lands. The app turns the big iPad screen into a very nice navigation device.
I really like how you get the moving map, a visual image of the intersection, along with turn directions all at the same time. The app will only work with the iPad 3G version. Pricing is unknown at this time.