I've used Super Springs and Timbrens. The Super Springs are laying on my garage floor now, the Timbrens are on the truck. I didn't like the ride with the $350 Super Springs, the $200 Timbrens don't affect the ride at all until you get a load in the truck.
All this talk about full vs semi floating and frame breaking, I have to ask "how much would somebody put into a 1/2 ton truck to get that to happen?" Put a 3000 lb + TC into a 1/2 ton pickup and you're going to have issues. Thats just WAY too much. Spring assist devices are very helpful to level out a weak-springed truck like the 1500 Chevy/GMC (and my Ford F-150...) with the somewhat overload (say, 1000 lbs over max, I hate to put a number on it), but I wouldn't put them on a Ram 1500 due to their weak frame construction.
Air bags can be very helpful on heavier pickups like the F-250/350 and 2500/3500 series, but putting them on a 1/2 ton is overkill and invites the truck owner to put too much load on the truck.