Clearly we're still a long ways off from the type of virtual reality experience we all dreamed of in the 1990s, but watching the video prompted me to think about the ways that current games, even the most "realistic" ones, abstract the types of real-world systems they simulate.
1. When you're running, it's hard to pay attention to anything other than what is right in front of you.
The player moves a pretty fast clip and it's especially impressive to see the treadmill keep up with him. However, he generally moves from point to point in short, linear bursts. In other words, it's the way you would run if your movement and your viewpoint were more dependant on each other. It's harder to keep your head steady when you're sprinting, which makes the weird run-strafing and constant mouse-looking that accompanies most FPS games much harder to pull off.
2. Moving while aiming is also hard.
This is related to the first point, but notice how how the player stops almost every time he needs to aim a shot. Even the most photorealistic shooters have players running and gunning, as it is usually fairly easy to remain accurate on the go. It reminded me of playing Receiver, since simply lining your shot was a difficult challenge.
3. Almost all video games obscure the "cost" of actions like jumping, crouching, or diving.
By cost, I mean the physical toll that extreme body movements take on your health. Again, it's easy to simply acclimate to a game's abstractions. Seeing military dude dive to a prone position down a flight of steps from a full sprint and then get up one second later no worse for wear is easy to write off when it happens repeatedly and when there is no mechanical consequence. Seeing someone's physical movements mapped so directly onto their in-game avatar makes me think about the possibilities for games to explore take a more limited, but more costly, approach to movement.
4. If this stuff takes off, I hope we called getting addicted to it "Barclay's Syndrome."