Although I have the Dension unit sitting in my office, I had the dealer ipod installed the other day. The woman told me it was a USB iPod interface and it was substantially more than the older kits. I believed her. Turns out it is just the old retrofit kit; no USB. Loads the playlists fast, but on my not full Nano, artists, songs, etc take several seconds. The sound seemed good the one time I used it. After they had to keep the car overnight to finish it up (after telling me it was ready), I had trouble opening the glovebox when I picked up the car. A little fiddling with the key got it open twice, but since then I can't open it to get to the cable. You can imagine my satisfaction with this.
Now, since the ipod interface emulates the CD changer, does that mean my car is "coded" for it and I could install the Dension?? Seems like it would be faster.
BTW, I asked the same thing of my dealer, that I wanted to install a CDC like device. Apparently the car really does have to "see" a factory CDC for coding purposes. They said no go.
My timing is really off, since I too would have taken a turn with the "factory" CDC for coding purposes.