How to view Software Update history?
Solution 1:
It can be found in an easy to read format using the system information app:
System Information.app > Software > Installations
System information can be found in /Applications/Utilities/System Information.app
or via Spotlight.
Solution 2:
It is not easy to read, but it appears to be up to date on my machine. You can find the Install history in: /Library/Receipts/InstallHistory.plist
Wouldn't it be nice it this were listed in the Update tab of the Mac App Store?
Solution 3:
/private/var/log/install.log
/Library/Receipts/InstallHistory.plist