i have never used one or even seen one in person. i thought they had adjustable limits so you can set the distance of travel to how ever far you wanted.I bought a nice one for $250. Wasn't impressed. Maybe if it only moved my light back and forth 2' it would have worked better.
There are 3 or 4 companies that make light movers. They can be expensive ones all the way to el-cheapo units.I experimented in 92, and bought a crappy little light mover, which would slowly move the lights back and forth. Do they still make these, and are they any better.