The 10.8.3 update is recommended for all OS X Mountain Lion users and includes features and fixes that improve the stability, compatibility, and security of your Mac, including the following:

The ability to redeem iTunes gift cards in the Mac App Store using your Mac's built-in camera

Boot Camp support for installing Windows 8

Boot Camp support for Macs with a 3TB hard drive

A fix for an issue that could cause a file URL to quit apps unexpectedly

A fix for an issue that may cause Logic Pro to become unresponsive when using certain plug-ins

A fix for an issue that may cause audio to stutter on 2011 iMacs

Includes Safari 6.0.3

For detailed information about the security content of this update, please visit:http://support.apple.com/kb/HT1222

See this article on how to validate this update.