Rotary blades are the thorn in my side. I have to use the Martelli ergonomic cutter because of hand problems, and their blades are expensive, don't last and half of them seem defective. I have to wonder if it's something I'm doing wrong. On the positive side, the cutter is completely easy on the hands. You have to use their blades in the cutter because the notches at the center of most blades will ruin the Martelli bolt.