I recently installed stabiloads from Torklift. It must be pointed out that there are two very different things made by torklift that are each named stabloads. I am not even sure how they spell that word but some idiot at torklift should have used their brains and named the two devices differently.
The ones I installed are the upper bump stop kind that engage the top overload leaf sooner. I haul huge loads of cargo in my truck and was regularly frame on axle without the stabloads.
I love them. They are a cheap and simple method to add stiffness to the suspension when under load. No leaks. No maintenance, pumps, etc. and I really didn't want to point load my frame with an air bag all in one place on the frame.