I have the direct predecessor to the ABC system (ADSII) in my SL600 and have had nothing but problems with it. That system is physically virtually identical to the ABC system, so I'd imagine my experience will hold true as the ABC systems age.

Only reason I haven't just ripped it all out and installed standard shocks and springs is because, when it's working, the ride is like NOTHING else. Very supple and comfortable, but still has absolutely zero body roll and great handling. If it didn't work so well when it actually does work, I suspect more people would just ditch it and go to traditional shocks and springs.

It's probably the single most expensive thing on the car to maintain, but at the same time it's also probably the single best feature about the car when it's working. The tandem pumps regularly fail, the nitrogen spheres rupture, the height and pitch/yaw sensors malfunction. It's a PITA, but you pretty much have to accept it since it really isn't the same car without it.