That is actually kind of what he does, but he/other illusion artists do use the technique that Shryke mentioned as well. I watched it on some "secrets of magic" or something like that, where, they show him doing the slightly lifting off the floor thing, then show reactions of peoples faces when he is doing something more amazing, then the editors cut and paste in the illusion artist being lifted up by some ultra-high strength cable from a crane-type thing.
Erm...I think thats right anyway, well at least part of it will be