You're right, those particular mappings were mainly for demo purposes. I guess it would be quite inefficient to use the approach from the video on a regular basis. If I used it in real life, I'd probably map the keys to complex macros, unmapped IDE commands, or other features that are hard to memorize on a regular keyboard.

In addition to @JoshTriplett's idea about velocity, I guess knobs and faders might have some interesting applications too.

P.S. Btw, it's a "she", it's my colleague performing :)