Slidefire makes a new one called the MOD. I have it on my AR. They fixed just about everything that was missing from the original. It is now 6 position adjustable, santoprene grip and recoil pad, QD mounts built in, 2 locks to secure it better when not bump firing, and is now ambidextrous.
I had the original and it was definitely a novelty. This one has the features of a standard adjustable stock....with a fun switch.