Also, I'm a recent convert to Clarence Ragland's "Kinesthetic learning" technique (previously alluded to). I challenged him by offering him a session with students at our club. In one session he had many students (including problem student and one heli student) flying literally Instructor hands off.
Even if the Ragland method is 100 times better than buddy box, I don't think it will become that popular. The problem is that it requires the instructor and the student to be very close and touching. A lot of men find that very uncomfortable. They are much more comfortable being a few feet apart with a cable between them. I know this probably sounds crazy, and it's not the kind of thing anybody would say anything about, but I believe it would have an effect.