I have the Load Handler 3000# version and the bed mat they sell. I have unloaded 1 to 1.5 tons (at a time, 4-5 loads thus far) of 3/4 inch bluestone, full beds of firewood, and a full bed of bank run (was way overloaded). Both of my trucks (old F350 and a RAM 2500) have 8' beds.
The only time I had an issue was a "duh" moment (my first time using it) with the full load of bank run - truck was on the side of a slope. As the fabric pulled the load to the rear, it started rolling on the bar uneven, got caught on the LH bracket and started to tear the fabric. Got the load off anyway, fixed the fabric with duct tape, and it still works fine.
A heavy load of damp dirt requires some effort on the crank - but still only takes 60-90 seconds. The bluestone rolled right off - less than 30 secs. The wood is easy too if it doesn't get hung up. I am still suprised how well it works
I do wish they had an adapter so I could use a 3/4 drive ratchet instead of the long handle. And I am going to devise something, like the plywood mentioned, to keep the load in the center of the bed - but if most of the material is centered when loaded, the leftover is only a couple minutes of work.
-Eric