Very interesting, I'll have to check into that! I use a Griffin FM transmitter right now, works OK, but has frequent problems with competing radio stations.
http://www.overstock.com/Electronics/Griffin-RoadTrip-iPhone...
http://www.overstock.com/Electronics/Griffin-RoadTrip-iPhone...
Once you hear the music from your device coming on your car speakers with out the need for wires you'll never go back.
Whats interesting that I learned about it once I got one came from the way I bought it. I made sure that it had a usb, a 3.5 mm jack, and bluetooth.
USB - sound quality is best but you have to use the radio user interface to interact with your device and play music, a ui which is terrible. Also on my HTC EVO the USB port doesn't stay connected reliably
3.5mm - not noticeably above radio quality still needs another cord
Bluetooth - better than radio quality audio (though not quite as good as the usb), no interference and no wires. I use this most of the time as not having to hassle with wires or the usb disconnecting interrupting the music is great.
ipod - Also almost forgot, if you use an ipod for your music most car radios nowadays have a special mode for them and the audio quality is awesome. (Like crazy almost CD if not CD quality awesome)
I use a Sony xplod personally.
Works very beautifully.