Look at USA Spec interfaces too
Since I originally posted on this thread, I picked up a USA Spec ipod interface for my car.
http://www.usaspec.com. You can get them at
http://www.crutchfield.com and some other spots on line, I bought mine at
http://www.cardomain.com. It's only ~$110 and while my car isn't supported by the monster cable it is by this one. My car is a Mustang GT with the in dash changer and none of the other ipod/cd changer interfaces will support it.
It hooks in to your CD changer controls and the radio's normal harness to pull power. There are no wires to cut and once you pull your radio it's about a 30 second install. You set up 6 playlists on your ipod and it can switch between those with the disc up disc down buttons. Next and Previous change the song. It charges your ipod while connected. There's no loss of audio quality going through it, it's just like listening to a CD. It does not break the existing changer, the CD button switches between ipod and the in dash changer.
I do have a few complaints, but it's all stuff I can live with.
Install it where you can get to it, because occasionally it looses it's mind and won't connect with the ipod. Audio will play over it, but it's not charging the ipod and you can't control it. The radio's display will look like it's continually seeking a song. Disconnecting the usa spec from the radio (power) will reboot it so to speak and then it will be fine.
It doesn't like the ipod to boot while attached, it will never connect that way. It seems the ipod must be booted and playing for it to connect well the first time.
Finally, it doesn't seem to charge/sleep it perfectly when the car is off. From day to day it works fine, I leave the ipod in the car and it starts playing right from where it left off. If I leave it in the car over the weekend, I'll come out to a dead ipod, not enough juice to even boot it. And since it seems to need to boot offline, I have to leave it connected for a while to get enough juice to boot, then boot it, then connect it. So now I just carry it inside for the weekend.