I've been using car handsfree bluetooth for 3 years, and have never had any issues at all....The connectivity is totally seemless from handset to car kit (back to handset if you switch off the car.) I originally had the Parrot system, but my porsche will have the latest Motorola BLNC system (released last week)....This is the first system to offer digit dial (you say a phone number and it dials)its fully interactive.....I wouldn't dream of purchasing the Porsche system (it's antiquated by comparison) The Motorola's chrome module will integrate very nicely inside the car (i'll post a couple of pics when its installed)
Here's the link to the Motorola BLNC website
http://www.motorola.com/automotive/solution_blnc.html