Apple updated OS X Mountain Lion yesterday. We now have an update for OS X Lion.

Changelog:

Resolve an issue in which icons in Launchpad could get rearranged after a restart
Improve Wi-Fi reliability for iMac (Late 2009 and newer)
Resolve an issue using Spotlight to search an SMB server
Improve compatibility connecting to Active Directory servers
Address an issue playing audio when a MacBook Air (Mid 2012) is connected to a Thunderbolt display
Improve Active Directory clients updating computer password and DNS records
Correctly update the keychain when changing an 802.1X password
Address an issue that could cause text input fields to appear black in some applications
Preserve iCal events when migrating to Microsoft Exchange Server 2010
Enforce managed preference based on a user’s primary group
Address an issue accessing secure websites when using a web proxy
Improve compatibility with RSA token used to authenticate with 802.1X networks
Improve compatibility with Centrify DirectControl authentication
Enable automatically logging into an NIS account
Support @icloud.com email addresses
Resolve a video issue with some VGA projectors when connected to certain Mac notebooks

Addition of Gatekeeper is one of the major change in this update. Gatekeeper was added in Mountain Lion to restrict app installation from the Mac App Store only.