The best feature was the load-leveling system integrated into the hydraulic circuit. If the car was weighted down with either people or cargo, the suspension system would automatically detect the extra weight. It would then compensate by further pressurizing the hydraulic fluid in the car, raising the front and/or rear ends to level out the car. Once the load was removed, the car would naturally raise up again, and the hydraulic system would relieve enough pressure to get back to a level ride height.
You really have to see it in action to appreciate it. Sadly, I no longer have the car, but I do have this video showing the GSA in all its hydraulic glory! Enjoy!