The # of 'blue arrows' is dependent on how far down or up you move the mouse. When you move the mouse to the lower or upper portion of the screen one arrow will appear, if you keep moving the mouse in the same direction (up or down) additional arrows will appear and the cube will rotate faster.
The quick select letters cannot be highlighted and selected with the keyboard, only the mouse. The same functionality is available by simply pressing letter keys on the keyboard, the cube will jump to that letter as if you had clicked a letter with the mouse. To rotate the cube with the keyboard you can use the PGUP and PGDN keys.
This functionality is the same for both Audio and Video lists.