The vid and comment from youtube just needed to be reposted...
The videos of these quadcopters are really impressive.
Video positioning information is captured by other systems in the room - and its all processed on several computers, then flight commands & correction info is fed back to the copter.
An earlier video shows some of the maneuverability and great flight control.
Here is one where the sensing is done from a hacked kinect sensor on quadracopter
https://www.youtube.com/watch?v=ToACDIXTzo0?fs=1