I don't feel it engaging--it's transparent. AD is always "on". If you've had Sports Packages in the old e53 or any other BMW pre-AD (meaning the option to add it as a stand alone as it was taken out of the Sports Package) it was already "built-in" the Sports Package which gave it tighter handling. I think when BMW made it an option they added to it the ride smoothing characteristics of it (ie smoothing out rougher roads).

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2008 X5 4.8
Jet Black/Black Nevada/Dark Burl Walnut
Adaptive Drive
Premium Pack
Tech Pack
Climate Pack
Sport Pack
20" Wheel Option
Premium Sound
Sirius Satellite
Rear DVD Entertainment
Multi-Contour Seats
Comfort Access
3rd Row Seat
Heated Front Seats
Running Boards
3M VentureShield Paint Protection Film