I don't personally have any experience with NH, other than reading articles about it, but I will share a story.
I used to ride at a dressage barn a few years ago, and a few months after I left it, they begin switching to Parelli. What started the switch was one of the teenage riders there bought a horse that was way beyond her skill level, so I suppose she was looking for alternate ways of training. The owner begin using it, as well as the boarders that were very loyal to her.
As time went on, they rode their horses less and less, and would sit in the indoor drinking beer while their horses wandered around them. That teenager that started it didn't ride her horse for about a year and half and then she would only ride it every few months. All the boarders that wanted to learn dressage were frustrated, since the owner refused to teach dressage anymore. At least half the boarders left, as well as most of the lesson students that had been riding there. Apparently lessons for new riders consisted of them sitting on their horses wandering aimlessly around the area.
This may have just been an extreme cause of them taking it too far, but it seemed like they were using NH as an excuse to be incredibly lazy. In my reading of NH, I thought that it was a technique to be used with your usual riding to make it better, but it doesn't seem like these people are doing much (if any) riding at all...