SQL Server 2012 BOL, under "keyboard shortcuts [SQL Server Management Studio]... list of shortcuts", under the section "Code Editor Keyboard Shortcuts" lists the "Action" for the keyboard combination of CTRL + R as "Show or hide the query results pane". This is the same behavior as SQL Server 2008 R2.
Pressing CTRL + R in 2012 SSMS does not perform this action. Instead, the status bar at screen bottom-left displays "(Ctrl+R) was pressed. Waiting for second key of chord...".
This behavior is consistent regardless of the keyboard setting under Environment of the Options panel in SSMS.