This may be a list of ultimately silly reasons, but I bought a snap-in adapter for my iPhone 4 because:
I hate having clutter lying about the cockpit (that's the pilot in me) and the snap-in adapter does away with cables and finding a place to put the phone, and
the phone charges very quickly when placed in the adapter, and
because I got it used at 25% of retail from a forum member, and
the iPhone was a free upgrade from Verizon from a five year old dumb phone so I really had no idea what I would appreciate, or not, about the "smart" phone and I wanted to give it every opportunity to prove its worth.
1HOT BMR's and BMWrules7 observations about the BMW Apps and signal strength and BT are 100% the same as mine. I don't use the BMW apps at all even though I have them installed. My signal strength was great before the snap-in adapter, and is the same after.
Would I do it again? for $50, yes. Just to keep down the clutter. For the asking retail price? Hell no.