Rich,

I've had Timbrens on the rear of my 06 2500hd since 2009 (when I bought it). I think they are great and work as advertised. As you state, when empty they don't contact the axle so ride quality is not affected. When loaded, the heavier the load, the more support they provide. Basically they 'self adjust'. I mainly tow a 5th wheel that has about a 2k tongue weight but have towed a heavier gooseneck as well. They definitely give the truck a more stable feel. Unless you really need to customize the amount of extra support each side gets, I don't see the advantage to a more complex air bag system. Hope that helps. Joe.