Me. Just ordered even though I was going to try my own rubber pad etc. then thought what the heck its not breaking the bank for the truck I love.
UPDATE: I received Springy Things pads yesterday and set about installing just two of them (they come four to a set), one rubber pad each between the top leaf and second leaf, pushed all the way into rebound clip and the gap between two leaves. I had to widen pads zip tie holes towards the outside because my AT4X leaf springs are wider. There was no space to get pads into the front end of rear top and second leaf springs. Prep for above: Raise truck body from rear by placing a jack under two bracket, this will help open leaf springs up a bit; expand gap between top and second leafs using a heave screwdriver or similar too; this helps easily slip pads between leafs.
Replicating one type of sound
when static: With the truck parked in the garage, I get under the truck, lay flat on my back towards the far rear end of the truck, pull down and push body from below and the clunk sound appears to be due to rear leafs rubbing against each other. I purchased the truck end of October, no sounds at all, then over xmas I drove through heavy snow in the mountains and even local, I believe the rear leafs have dust or something accumulated between them; done only 3500 miles from new.
Another sound when moving: when I drive and turn left or right very slowly <2mph, in forward or reverse, I hear a groaning sound from the rear, amplified by the empty bed. Almost thought bolts holding bed to chassis may be loose, I have not verified that yet.
In any case, with two pads installed, I need to take it for a drive to check if anything has improved; else I'll take it to the dealer again and explain/demonstrate the sounds and perhaps have them agree its leaf springs and get replacments (if I'm lucky).
2nd Update: Appears to be much better; exhaustive testing pending
Pics below: The white stuff is just grease I was trying from last week.