i'm not doing this just to lift the back of the truck 2 inches, the main reason is so i can pull the trailers i need to with out it saging so much.
then get air bags and be done with it. then you don't have the rear end jacked up all the time, only when you want it to be.
air bags ruin the ride though, I got my AAL's on and pulling a 3-4 ton trailer, the ride is still pretty smooth
I also have an AAL, it works great, towing is not a problem and at first the ride is really stiff but once its broken in it gets better.