Well, I am by no means an expert, but I have dropped about $3000 into the ADS in my car, so here are some observations. First to check are the gas spheres. There are four, one for each wheel, and mine were all bad.
This is the main cause of the harsh ride. The spheres are relatively cheap,
I think around $280 total to replace all four. But every other component on this sytem is priced as if it were made of plutonium.

I paid $960 plus $300 labor to replace a leaky distribution block. The block looks like a brake master cylinder, but with no moving parts. $960. I paid $1350 to replace a leaking leveling valve. There are three others that I have not touched.

If you really like this system, which I obviously do, take a run at getting those spheres changed. It's cheap and it may solve the problem. If not, I would yank the whole thing out and install conventional springs and shocks. This can be done for about $1600, there was a post about this on either this site or the mbworld.org forum. That is my plan if another four figure repair should crop up.

Don't get discouraged, this system is complicated but not impossible to fix, just decide how much it is worth to you, and remember you can always bail out and just put in regular shocks and springs.