Joe, its usefulness only comes about if you use a pure swinging motion, its not a tool for hitters. The reason i bring it up is because of the way it must be used to keep the saft straight. If it has any bend in it, the ball curves, so it will teach you (if you let it, i seem to have a problem letting it)how to stress the shaft length wise, Swinging.
Thos os one of the many things i dont understand, shaft flex, if we are hitting in any way, i can see flex playing a part, because we thrust the shaft from the side, but in swinging, we are told the club is stressed length wise, why would flex matter??