About twelve months ago I bought a new car and installed some basic necessities: alarm, central locking, and a better-than-factory stereo. For the stereo I picked up the now superceded Pioneer DEH-P4850MP "CD Tuner". I chose this model because it had good features for the price bracket and Pioneer seemed to have the best iPod support at the time.
Pioneer's iPod integration came in the form of the CD-IB100 II interface adaptor, a small module with the iPod dock connector on one end of cable and the Pioneer proprietary P-Bus connector found on most Pioneer car stereos. With a quick specialist installation, I had my iPod 30GB Video ready to crank.
For playing the music collection on my ipod through the car speaker system the Pioneer setup is great. For seeing and controlling what I'm listening too, there is definitely room for improvement.
The head unit has a 16-character alphanumerical display that scrolls artist and title information from audio discs with CD-TEXT. The iPod has full ID3v2 artist, album, title and all sorts of other information for each song. Combined the Pioneer equipments works together with the iPod to present the first eight characters only. I have it set to show artist because eight letters of a song title are quite useless but William Hung, William Orbit, and William Shatner are indistinguishable on the display.
The head unit also allows (forces) you to navigate the songs on your iPod via the stereo controls or the stereo's remote. You can navigate by artist, album, song, genre and even iTunes play list but after every press of the next or previous button, there is a delay while the iPod seeks to the first song in your selection and starts playing it. When you're listening to Bruce Dickinson and want to switch to Nick Cave it is very painful waiting for each of the artists in between to start playing before you can push the skip button again. The Pioneer iPod adapter is a great example of electronic hardware engineers developing end-user software.
Thankfully, while the iPod's built in controls are disabled when connected to the stereo it is really easy to disconnect it to queue songs the normal way or to take the iPod with you when you leave the car. The iPod also does a great job of remembering the current position in the current song when you turn the car off or disconnect the iPod.
Ultimately I'm happy with the system and have created five basic mood-oriented random play lists to minimise navigation pain. My fiancee isn't as happy though as most of the music is mine and while I like to listen to some more obscure stuff, she prefers mainstream songs.