I can also see a use for keyboard shortcuts: Press lightly to delete a letter, a little harder a word, harder still a line, and really hard for a paragraph.
4 levels of modulation might be too much for accurate use, but three should be workable.
MIDI keyboards taught me that this channel is very hard to use effectively, even with tons of keyboarding experience. It's cute, but I'd need a lot of convincing it's very useful.
I would save up system notifications, so when you're really in the swing of typing and REALLY FURIOUS, your system would freeze momentarily and a cheerful avatar would popup and ask you about updating your antivirus program or tell you you have unused icons on your desktop.
I see several subtle uses for this in day-to-day applications. When holding down the arrow keys, it would be nice if my cursor moved faster if I was pressing harder. Same with any key repetition. Right now, repeat speed is time sensitive, so if I'm backspacing to delete an entire paragraph, I need to wait a few seconds for it to speed up. Then I have to time it just right to prevent overshooting and deleting more than my target paragraph.
Another practical use--I wish my Tivo remote had pressure-sensitive keys. I could zip forward then gradually back off as I approach the end of my commercial block. Just like one of those professional video editing systems, where the operator has total control of how slowly/quickly they can zip through the video.
They should get rid of the "typing harder makes your letters bigger" part of the demo. It made me cringe.
The "low-resolution multitouch" thing was interesting. I would really like a keyboard that doubles as a touchpad. I want a mouse closer to my fingers. (but I hate the nub)
Other than that, adding pressure sensitivity to a keyboard isn't innovation, finding a good use for it is.