I have this a while now and have been pretty impressed with it for the most part. I installed this to our VW Touran and it was pretty much a synch thanks to some of the great guides out there on the web showing how to remove the factory stereo (TD300 I think).
Once I got the stereo back in place and ran the ipod connection cable I tried it out, by hitting the CD button twice I got to the CD Changer input which is essentially what this device uses.
Pros
Easy to install
Seems very reliable no glitches yet
Good quality sound
Keyed cable connector so no confusion as to where it goes
Reasonably small and light in size
Also you can still use your existing single CD player
Cons
You'll pretty much need to use the ipod itself to control the songs playing if you have 6+ playlists, so maybe not that suited to hiding away in the dash compartment. I have mine in the central pillar by the gearstick.
Thats the main gripe I imagine folks will have i.e. playlists equate to one CD in your CD changer. If you exceed that no. i.e. 6 CD Changer with 6+ playlists in my case it seems to do strange things on the stereo display. That said it responds exactly to direct iPod control and has never frozen or refused to play songs.
So to summarize excellent device missed out on 5 stars because the stereo head unit control functions are a bit limited, especially with lots of playlists.