It is one of the single best aids to teach you how to synchronize the hands and body through the shot, not to mention the benefits of elbows pointing down and staying the same distance apart (plane).
Personally, I like to use it much lower on the forearms, near the wrists. This really allows the 'set' feel of the wedges, without 'limiting' the motion that can happen when many try to use it.
I use a flexible stretch version that I can twist to fit down near the wrists.
Best used WITHOUT a club and/or with a heavy club- focus on your pivot. As with many training aids, it is biased towards a swingers motion (pitch elbow) and can be a useful way to learn a proper startup swivel.