I have a Renault Tunepoint car kit. iPhone original and 3g both didn’t charge through it, but 3g under 2.1 suddenly does. Very strange. I know 3g has dropped firewire charge support common in car kits, but neither iPhone charged so I’m not convinced this was the issue. Perhaps greater backward compatibility with previous 3rd party accessories? Strangely, the nag screen about non-compatibility still appears though… All said, very unexpectedly pleased.
Found this earlier: "No its annoying really, the iphone orginal charged of the 12v firewire pins, however *** 3g version charges over the 5v usb pins."
Problem solved: http://store.apple.com/uk/product/TS696LL/A?fnode=MTY1NDA0MQ&mco=Mjg0NjU4Mw
Although for that money I think I'd rather buy an in car charger!!!