I have one, and have shot several thousand rounds with it. 90 % ???? Well, let's not get carried away, the way an advertising guy might.
It is effective in reducing percieved recoil. It is also difficult to get a proper cheek weld on, and it doesn't line up for a lot of folks.
While the ability to shorten the stock seems like a good feature, when I did so, I got a badly bruised cheek.
I hope you enjoy yours. I am thinking seriously about removing mine and replaceing it with a wood stock with a limbsaver recoil pad.
I know from experience that I can shoot much more accurately if I can acheive a good cheek weld.