For any who may still have an interest in this discussion, I checked out Gary's concern and the Assignable buttons make viewing the lyric and other displays or functions easy. Using the Assignable buttons, I was able to quickly display the score and lyrics just by pushing a single Assignable button. Also you can immediately jump between the displays, including displaying the VH status over whichever display is up.
SX900 Assignable Button Demo Hope this helps others who may be wondering about the utility of these buttons.