Works great for me, makes the crossbow easier to carry and leaves your hands free. It needs a slight adjustment on the harness near your lower back, a way to anchor the base of the crossbow, it can move a smidge, but they will probably have an improvement on that in no time.
Buy the regular sling!! This is very hard to get on and off, while being very uncomfortable when on. No instructions on how its suppose to fit, so you only get a tiny picture of someone wearing it to go from.