Is my local BMW shop manager an idiot??

[barbja]

Sometimes its hard to tell the difference with normal driving.

The best way that I can tell that its 'working' is to go over a successive set of speed bumps in a parking lot at a 'reasonable' speed (ie, faster than most people go over speed bumps). Turn the sport on and off between each bump. With it off, it will be pretty bouncy, with it off, it'll be stiff (and if you're going fast enough, you can bounce things in the cargo area off the roof!)