Very clever! I hadn't fully understood the mechanical complexities involved in a standard single-rotor helicopter. I just thought that they were hard to fly manually (which made me very confused to see all the computer-controlled quadrocopters - why didn't they use just one rotor?)
Well the issue isn't just that they're hard to fly or that they're mechanically complex - the issue is that they're both. So you crash often (when flying models) and crashes are expensive. This makes it a very expensive hobby.
The issue when flying is that they balance as if they are on a ball. You need to constantly adjust the controls to stop from "falling off the ball". Go the wrong direction and you speed up the rate at which it falls. When it is facing away from you, that's not very hard. When it is facing towards you everything is backwards. When you are turning, the correct direction to stay balanced is constantly changing.
Automated systems can do this automatically for you though, so a drone-like autopilot in a standard helicopter could make them as easy to fly as quadcopters. Traditional helicopters are still mechanically complex though. This system looks to fix that. And this would be more efficient than a multirotor.
