Hi Peter, as well as paying top dollar for the adaptor you also need the Apps extra software installed,about £200 on the options list, not sure how much to retro fit. For my own use the only benefit would be to be able to control the Internet radio on my iphone via the idrive rather than the phone itself and better menu for the phones music and podcasts. Yes I'd get a better signal but it's easier to charge the phone via a USB lead in the armrest than have to take it out of its case to plug into the adaptor.
I don't have the Apps option fitted, so may find out how much I'd get fleeced for this rather than also £130 for a bit of plastic.
Afaik you don't need the adaptor to get the full use of connected drive if you use a USB lead. Am I correct?