iPhones and MR2s

I know a few of us here have iPhones.

I just got myself an iPhone 4. i've had a first gen iPhone for the past two years and my stereo has been charging it and playing music very well.
now with the new iPhone, my stereo doesn't charge it (similar to the way that old docks dont charge new ipods/iphones)

How do you use yours in the car?

aux input to your stereo, direct ipod connection (USB or specialised connector?)
windscreen mount?
used as a GPS?

I recorded my movements for the day on GPSx - the iPhone just left the GPS running in the background. it was pretty damn cool actually [:P]