Technical editor, Phil Ryan, actually got some hands-on time with an early model of the new lens and found the Pro additions very enjoyable. The metal ball makes moving the optics far smoother, getting rid of the slightly "scratchy" feel associated with the plastic ball. It also does a much better job of holding the optics in place during focusing, even if it's not totally locked. As a result, you get more consistent performance and quicker transitions between shots. You don't have to be a pro to appreciate that.