I just received on of these in the mail, and thought I'd share. I have no financial interest in Brass Stacker; they just make good stuff!
Pretty nifty I think. I never had any real trouble manipulating the cocking piece. My fingers did, however, get a bit sore after a bit.
This adds a lot
of control to the safety, and one can lower it into place silently. Excellent for hunting! They carry a black version as well.
This is available at my place, or at http://www.brassstacker.com