It's astonishingly elegant. I can't imagine nobody's thought of this before, so it's likely that the implementation is harder than it appears.

The added weight of the cage and gimbal system likely required them to use expensive ultra-light material and extra strong electronics. The motor on this thing looks pretty beefy, which in turn would require better driver components and a bigger (and/or denser) battery.

That said, I hope they can get a production version (made of syrofoam maybe?) so I can play with it. My main issue with hacking on quadcopters is how fragile they are.

I wonder if there's a "gimbal lock" equivalent where impacts in certain alignments relative to the gimbal mechanism still transmit a fairly large moment to the central unit.

If you have to take care of that situation, maybe it would be better to take care of all the impact compensation in software, and save the weight of the gimbal mechanism.

I've seen a few that looked a lot like this actually. For example:

http://www.amazon.com/ROBOTIC-3-Channel-Flying-Ball-Helicopt...

The main difference in the research here just seems to be the separation between the outer ball and the stabilized machinery inside it.