In AutoCAD 2010 I frequently have a need to place 2 drawings side by side (tiled vertically). I find it somewhat inconvenient having to find the command in the Window panel of the View tab so I added the command to the Quick Access Toolbar. 

How I made the change: I went to the CUI editor and found the Tile Vertically command within the Ribbon > Panels.  To add the Tile Vertically command to the Quick Access Toolbar simply drag the command from the Ribbon > Panels > View-Window … while holding the Control key down (to copy the command rather than moving it) and drop it on the Quick Access Toolbar.

Most of the time I want to use Tile Vertically.  Sometimes I want to Cascade more than 2 open drawings.  After running the Tile Vertically command I can immediately hit the SPACEBAR key (acts as an ENTER key) to repeat the command and choose one of the other options available like Cascade or Tile Horizontally.   The SYSWINDOWS command is the underlying command which makes the Tile Vertically option available. 

To find more info search the AutoCAD help file for the topic “Switch Between Open Drawings”.