Interesting demo. When I took a quick look, I couldn't see the demo. Then after it had been going for a couple minutes and I just sat back and toggled the button while staring at the screen, I could see the difference as clear as water and sand.

That makes me think that it's a training & focus thing. Much like with MP3s, if you concentrate on the picture quality, you can see the difference. If you're just watching for the content, you can't. Most casual web viewers are looking for the content.