The setup works well and of course charges the phone at the same time. The biggest benefit is being able to control the music from the head unit in the same fashion you control the CD.
I originally had the C33 head unit with a casette tape, but the one I had was apparently manufactured by BECKER and the Becker units are not text capable. I swapped it for a BMW Business Radio C43, which has the single CD slot and also the CD controller port at the back. It is very very important to ensure the unit you have has the CD changer port on the back as that is what allows the Dension unit to work its magic.
The benefit of this is of course that whilst I mainly use the iPhone, I can, if I so choose, also play a CD.
This, and the HID headlight upgrade were two of the most cost-effective mods I have made to the car.
The Dension units can be either purchased directly from the Dension website, or the way I got mine, through eBay. Not too sure of protocol so I won't mention any vendors here, but I am happy to supply name of vendor I dealt with on eBay via PM if required - I can HIGHLY recommend this particular vendor, they dispatched quickly, and their after sales service with regards me finding out about having a Becker unit and what to do was absoluetly first class - I couldn't rate them highly enough.