We've put them on 3 trucks. Paid $250 a pair from a wrecking yard in the mid-west. They came off of school buses. Two bolted right on, one set had to be heavily modified. It takes quite a bit of fiddling around with them to set them up.
We set the contact patch about 3.5 to 4" off the ground and about 1/4 inch ahead of the axle centerline. Set up this way, the chains cover about 75% of the inside tire. You can get more coverage by lowering the point at which the unit touches the tire, however they say that reduces the depth of snow at which the chains are useful.
I haven't used them in the snow yet, however during a build we had to juggle trucks and drove a stretched truck with no box up a fairly steep hill behind the shop. The truck lost traction (no weight on the back end), I engaged the locker, it went a few more feet, then just spun. I deployed the chains and it went right up the hill! I'd really like to try them in the snow.