I bit the bullet & got a Skier's Edge IV after I spent a week last spring at Whistler and found that my leg conditioning just wasn't up to the opportunities of dropping repeatedly into the bowls on those two big mountains.
My trip out to Whistler 2 weeks ago was a different story---I was able to pay attention to developing better technique in the steeps and bowls, rather than dealing with my quads blowing up on me. And as Arby mentions, the machine gives you good practice in keeping a quiet upper body and working on knee-through-hip angulation.
I don't think that my own use of the Skier's Edge has helped with my release moves. For me, in fact, the machine seems to encourage a "stomping" pattern to weight shift and foot control that I have to consciously avoid when I get out on the mountain.