Dave I have an older variant of that device and it actually works really well. It is very hard to use effort wise with all the springs. If a person is cocky strong it is one of my favorites for saying why don't you try this (with me usually saying it is not too bad). And they get angry when it does not move with all the springs attached.
The only bad thing is that it scares the hell out of me when I use it. The springs creep, squeal and yell and I feel that I am about to be hit in the face and eyes with exploding shrapnel. I do like it and it has not exploded yet. The one you show added some hand grip type holders to keep your hands from slipping off. I would imagine that was done because it must have slipped out of people's hands with bad consequences. Mine was made in Korea and it is pretty heavy duty and high quality. Not sure how any knock offs are out there and how they work or feel.