The page up/down keys do the same thing as the left/right cursor/arrow keys, that is, scroll through the sections on the now playing display.
It would be nice if the page up/down keys (and /or the up/down arrow keys) scrolled up and down the text of the currently displayed section (album review or artist bio).
This would make the 10 foot user interface much more useful and cooler to show off for guests.
