Mac OS X record of installed software (including operating system install)

The file /Library/Receipts/InstallHistory.plist contains a full record of installations, some details about the installation, and date of install.

I stumbled across this today and thought it could come in handy with regard to certain situations.  I just wanted to note it in case anyone else didn't know about this file (like myself).

One potential use I see is finding out what the initial operating system version was for the Mac.