I miss the ability to press Command-D key to trigger the Don't Save button when closing documents. So, I wrote the following short Applescript to regain that functionality.
Paste the following script into AppleScript Editor and save it somewhere. Then use QuickSilver, Fastscripts or some other keyboard shortcut utility to trigger this Applescript. I set Control-Option-Command-D to be my shortcut. I can now trigger Don't Save with a keyboard shortcut.
tell application "System Events"
set frontApp to name of the first process whose frontmost is true
set focused of (button 3 of sheet 1 of front window of process frontApp) to 1
tell application "System Events" to keystroke space
end tell
[kirkmc adds: A previous hint offered a different AppleScript, and the comments include a Terminal command to turn this functionality back on, if you prefer.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20120314113133816