These parrot kits look like a viable option for adding bluetooth

http://www.parrot.biz/usa/products/ck3000evolution
+ the BMW steering wheel kit
http://www.parrotkits.com/steeringwheel.html

The total for the parrot bluetooth module and the steeing kit is <$250. It seems like once hardwired all of the functionality of the OEM unit is in the parrot kits?

So my question is, what is the real benefit of adding the BMW module for about $750.

Has anyone installed one of these bluetooth kits and are you happy with it.
Thanks