Our 1990 Winnebago Warrior came with them - the original owner had them installed. It is an HWH system and still going strong 25 years later.
I love them. Leveling is a small part of what they do. The big thing they do is they stabilize the camper. Otherwise, every time someone rolls over in bed or otherwise moves around the camper the house bounces on the suspension. With the jacks down, the house doesn't move. It's very nice.