I wouldn't say terrifying, but pretty crazy to watch in action. What is terrifying is the thought of seeing a bunch of people watching TV like this.
You'll see what I mean when you watch the video:
http://www.engadget.com/2011/01/15/man-discovers-glasses-free-3d-tech-in-the-blink-of-an-eye-video/Interesting concept, interesting execution, freaky to watch. Make my eyes hurt looking at it.
EDIT:
Just for the hell of it, I can mimic what those things can do, sans them (naturally, albeit at a rather low frequency, but should e enough to experiment with). I now need a 3D video/media to test it out on to see if I can pull it off. I can just say that like other 3D glasses, doing that method will slightly darken your overall vision (while applying it), but the concept looks like it can work.
EDIT EDIT:
One idea immediately came to mind. I recall the Sega Master System used a similar 3D system with alternate blinking (the 3D glasses used that method with LCDs). I can try to play some Maze Hunter 3-D, Blade Eagle 3-D, or Missile Defense 3-D, and see if alternate blinking really fast can mimic the 3D effect implied in this video. Worth a shot. The refresh rate is the only challenge to mimic.
EDIT EDIT EDIT:
No luck. I can't asynchronously blink fast enough. Even at 60 FPS (emulation speed) and 60Hz monitor speed. Not to forget, like I mentioned before, synchronizing to the frames alone is a challenge. Only once or twice for half a second did I get a solid image, one version per-eye. Not enough to see enough of a difference however (even pseudo-3D).
At least when trying out the method sans device, at least I know that the guy demonstrating it was comfortable. Didn't hurt, just hard to accomplish without rapid pulses to the eyelids.