Not on an F250 but on an F150 for a TT. They will raise the rear about 1" unloaded. They worked as advertised. I have had all three types of load enhancing devices. Air bags, Timbrens and Supersprings. Out of all 3 I would go back to Airbags. More money but not a lot more. They need to be run at 5psi min so that won't affect the ride. And can be adjusted to level the truck back up.
Supersprings have no adjustment to speak of. There are different holes for installation that will affect the load some. But for the most part you only get what the springs give you. In other words depending on the load they may or may not give you what you need. Air bags will keep on giving.
Timbrens won't change the empty ride at all. They are set 1" above the axle so when your load is in the bed the Timbrens come in contact with the axle and the truck really never settles anymore than that. At least in my case with 1800lbs in a Ram 2500. I find the ride a bit harsher with the Timbrens than the air bags.
FWIW I wouldn't buy SS again. Just not enough flexibility.