I had one for my regular sewing machine. I used it a few times. I took it off for some reason and never put it back on. I have no idea where it is so I guess I wasn't impressed with it. My friend uses a laser when she pieces. It is a feature on her machine not attached to it.
I remember something. Mine was attached and if my machine had any vibration at all the laser beam would jump around. I had to sew very slow.