First of all, I know that you can't use a keyboard to play games. That isn't my question.
I question whether or not the keyboards have anymore functionality other than typing messages. I have played around with mine for a while, and discovered that the spacebar, ESC key, arrows, and Windows button have uses with the 360. Them being: ESC = B, most of the time, spacebar = A, most of the time, the arrows navigate up, down, left, and right, and the windows button activates the guide button. Only the Windows button would have functionality during a game.
Is there any more that I missed in my experimentation? I had a chatpad once(I don't know where it went...), and I remember a windows live messenger button. Maybe there is a function that opens that as well? (CTRL + Windows Button would be my first guess)