If a button is pressed between the time Menu is pressed and released, it would not need to bring up the menu
Menu + Lock = take a screenshot
Menu + Up = the first game-added menu item
Menu + Left = the second game-added menu item
Menu + Down = the third game-added menu item
Menu + Crank = controls volume
That leaves Menu + Right / A / B for games to assign on their own
And I'd like to suggest long-hold Menu for a universal custom soundtrack menu that plays files in the music folder.
One reason for this is I've seen some people complain that that while the menu helps make up for the lack of buttons, bringing up the menu takes focus away from the game so it can't be used in-game