Hey!
I've just built and tested this on my breadboards and it worked right away 
Really cool, thanks for sharing this!
I have a question about ascii coding of individual buttons. I have tried to reverse engineer it but it's so random i can't figure out the logic behind it.
I want to use 2 of these keyboards in a project but can't seem to run them in "parallel" since defining new buttons also requires to define them with some other ascii code than the one already used.
If anyone has any idea on how to run two keyboards on the sam arduino i would be most happy if you would share it.
Thanks!