I watched the video, and it's incredibly irritating. About 30 times or so, they show the mower going up to a post, and then they cut away. They never show the one thing that is interesting, how the thing goes around posts. I couldn't help but think, what are they afraid of showing?
Based on the snippets of video, I suspect that the thing doesn't swing back fast enough after it swings away from a post. If you just go at a constant speed it will leave unmowed patches behind the post. If you want to mow completely you have to either stop or back up.[/QUOT
I would guess you can either stop or backup or most likely you would have to mow on the opposite side of the fence which would allow you to get the grass/weeds that were missed. Could be worth it if someone had miles of fencing that needed mowed I guess.