Hey Skuff,
We have about 30 of these light rail systems setup in our winter greenhouse. I wouldn't expect a rise or loss in yeild it says its better but I have never seen results to match that. It DOES however work for reducing the number of lights or increasing the amount of area a light will cover. Its fairly easy to use one light on a mover versus 2 fixed lights even 3 if your vegging. It also depends on how far your moving your light we have ours on 2 rails so they travel about 11 feet. Results may be different on a single 6 ft rail.
It might be just a random thing but I did seem to get more stretching from most of my plants. They have a pretty good longevity only one broke in about 3 years. We made our own rod for mounting the hoods versus buying the ones on the site. If your a DIY person I'd suggest that. Good luck if you have any other questions let me know.