I have one on my Bernina Artista 200. Once I finally learned how to use it, it quit working!!! My dealer owner adjusted it and it works perfectly. He said sometimes they just get tweaked a bit and it causes it not to work. He is the greatest and he fixed it for nothing in the middle of a class I was taking.
I am sure transporting my machine back and forth to classes, etc. give ample opportunity for it to fall out of adjustment.
Since age is beginning to affect some of my vision, I do appreciate the help of the machine. To press a button and have it done would be VERY nice!