IF you follow directions and exercise some care, it will not leave scratches on your blades. It comes with an instructional DVD. WATCH THE DVD! In fact, watch it two or three times before you ever set up the Sharpmaker, as you will doubtless miss things the first time or two. Watch it again after you set up and use it a little.
It is pretty simple to use, but there are a few tricks to getting the best results out of it. The two biggest that I know of are:
1) End each stroke with the blade tip still in contact with the stone. Dragging the tip off the stone will round it off very quickly.
2) Use VERY light pressure. Most of the problems I read about here are probably a result of using too much pressure on the rods in an attempt to hurry the process. It doesn't work. Just let the abrasive do its job.