I have the Hip-Belt from Ironmind, it's a really thorough leg exercise. I have the loading pin which allows upto around 200kg to be used depending on the size of the plates.
The big problem for me has been the set-up. It's just so much hassle to set up relative to any other barbell or dumbbell exercise. I use a couple of cinder blocks to stand on, and take the weight off a bench, I then hold the rack supports for balance.
I know McCallum was big into these, if I had a place to leave it set-up I probably would use it more often.