Some of the Keyboard Shortcuts in 2010 that would be useful are missing or just are not he same as the ones that were in 2009.
You can add/edit to the KeyboardShortcuts.txt file that should be located here on your computer:
C:\Program Files\Autodesk Revit Architecture 2010\Program
Most of the commands are already in there (though it may take some scrolling to find them), but they have a blank value. Just put in the initials you want for the shortcut in quotations following the same format as the other entries.
So I changed these two lines
; "" ribbon:"Detail-Detail-Masking Region"
; "" ribbon:"Detail-Detail-Filled Region"
to this to get Filled Regions and Masking Regions to work.
"MR" ribbon:"Detail-Detail-Masking Region"
"FR" ribbon:"Detail-Detail-Filled Region"
After saving your modifications you have to restart Revit. The shortcut initials that you put in will also show in in the roll-over help menu when your mouse is above a command in the ribbon.