Steve, we also just got a wagon (the Windstar is GONE
). Opinion of other owners on web is that mostly the spheres go bad (lose gas charge internally) then the ride gets bouncy (compressed gas is the shock absorbing medium). The struts are usually not bad. I would not swap to a conventional system. I can confirm that the springs are different capacity (H&R lowering springs are different for conventional and hydro-pneumatic systems) as Jimy stated.