Would be nice to have volume levels auto-compensate for increased road noise like the high-end cars do. Obviously would require a mic installed, but my plan is to put one in anyway, use a D-link Bluetooth dongle to communicate with my cell phone (still in my pocket) and have speakerphone over the car stereo. There is a bundled application called "Headset" with the D-link dongle that achieves this beautifully.
Anyway, thought I'd throw in the request. :)