I have to transport three kayaks at a time, getting the kayaks up on top is not a real problem, but tying them down can be, this looks like it would work for that application, attach the kayak racks to the the cross beams, load the kayaks tie them down and then draw them up on the vehicle, pure genius.
If I had a bad back,or wasn't strong enough to carry the boat then I could see it. But if you are not strong enough to carry it or have too bad of a back what good is it to be able to get it on and of the truck? I wouldn't be able to carry it to the water.
I'm just the kind of person that 19hawk11 describes. I have a herniated L5 disc, and cannot lift over about 35 to 40 pounds. This type of set up really would not help with the size boat they are showing, as once it was on the ground I couldn't move the boat. For a lighter weight kayak you could transfer it to a kayak cart, but for a boat this large I would trailer it. Just my two cents worth.