The overswing has always been my nemesis, but that does not mean it in itself is bad. As the others said, if all your positions are good than there is nothing wrong with it. If you get there by raising up, bending your left elbow, breaking your wrists, or any other way, then look to change it. The only thing that has worked for me is to go to Homer's Hitting procedure. Presto. Shorter backswing.