I've been about a putt per round better. Now, let me throw in a caveat because I don't know that the improvement is entirely due to the moving-ball-marker-gizmo and might be more due to their plastic-line-template-gizmo.
In practice, the line markings with their line template helped me identify a way to roll the ball more on a 12-6 plane. I had a little bit of wobble in my roll that i wasn't seeing with just a simple, single line. I had some mechanical flaw in my stroke and my line wasn't rolling 100% 12-6. I didn't visually pick that up until I started using their line template which has these little side markers/wings which showed this slight wobble in the roll. I feel like this mechanical change has me rolling the ball straighter and that is probably the biggest part of the improvement. I feel like I'm simply rolling the ball straighter.