I have a friend that has one, it has some issues. The stock doesn't lock open, or stay folded as well as it should, and the leather cheek piece is not quite as good as the original. It appears, at least to me, that the pistol grip circumference is a bit larger as well. There were also some issues in the way the band fits to the stock relative to the retaining spring. Most of what I mentioned could probably be fixed, but for the price, you'd expect it to be good to go upon installation. Anyway, I gave his a try at the range, and as you might guess, didn't like it. They are not really all that comfortable to shoot. It excels if all you want to do is carry it around folded all the time.
If you're looking for something that's more usable than M1A1 pattern correct, then buy a Choate Machine & Tool M-1 Military Side Folding Stock. I had one years ago, they are much better all around for a rifle that actually gets fired. However, if you absolutely must have that period M1A1 look, then buy the Italian knock off sold by Marstar.