I have several Bernina seam rippers and have NO complaint with them at all. I keep one in the container with my pins, so it doesn't roll off my sewing table. Also keep a large rubber band around my pin container so the container doesn't "creep" off my sewing table from vibrations.
Also, another tip: I keep a piece of that rubbery shelf liner on my sewing table and place my thread stand on it so it doesn't slide or creep.