I have been tournament skiing for nearly 25 years, and still love it.  My list of injuries sustained during those years is too long to describe in detail, but the major issue has been two lumbar disc surgeries, the last as recently as 2007, and then a cancer dignosis last year.  fortunately I am in remission, and looking forward to my first full season on the water in two years.  For myself, there is little doubt I could not continue to ski  without the powervest. 
Those who feel this is somehow cheating,  the vest does not make up for bad technique or poor physical conditioning.  What happens is the load placed on the mid and lower back is distributed to the hips, a major skeletal component.  In fact, my performance was decreased until I adapted my skiing to it's unique load distribution.  If you want to prove how tough you are, then I assure you years of skiing will beat you up like few things will.  So feel free to complain this is cheating.  Keep at it long enough and you too may think the powervest is a good choice.  I do not wish my injuries on anyone, but this sport WILL destroy your back over time.  Detractors of this vest would probably not ski without gloves, would they? Everybody uses a Carbon Fiber ski, is that cheating?  I bet you wouldn't want to give up your carbon fiber based slalom rocket for a 20 year old glass ski.  Does anybody complain when a skier shows up with a knee brace?  How about a pro football player who tapes his ankles? 
I am convinced the vest significantly decreases the risk of chronic low back injury, and plan on purchasing one for my 15 year old son as well, I don't want him suffering the same back problems I have had to endure.   This is innovation of our sport, and I am thankful this tool is available to me.