I got my X535d on Friday, and I was wondering the same. In a sense, it's too bad that it's always on, because there is no way to do A/B testing (Adaptive Drive On / Adaptive Drive Off). This makes it a difficult option to justify spending $3k for....

Having said that - I got it because I want my luxury ride to feel like a luxury ride, and with Adaptive Drive it does. Tremendously so.

No body roll in corners, no yaw when braking. It's funtastic.