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.
Other than that, adding pressure sensitivity to a keyboard isn't innovation, finding a good use for it is.