I have never used one.
My thoughts about them are: the gas tube gets hot, the gas tube moves, and it is too far forward. I assume that you are thinking about using a red dot. Red dot or scope, I would get the Choate and drill and tap if I HAD to have a scope. I made a knockoff with a piece of angle steel, JB Weld, a Mossberg Weaver mount, and a drill press. No matter what anyone says, my 2 cents is that scopes don't work on SKS's. The receiver is too high for scope alignment. You could try European style "no cheek on the stock" shooting....it just doesn't work very well.
I love my SKS though.