I almost never use the arrow keys. They're for scrolling through highlighted things in a book, such as a table of contents, or footnotes. If you see an asterisk that's highlighted, if you press the button inside of the arrow keys, it'll take you to the footnote (then you have to hit "menu" and "continue reading" to go back). If there's more than one footnote on the page, use the arrow key to get to it.
That's pretty much the only experience I have with those keys...