While the download is called OS X 10.8.2, just like the most recent update to Apple's current operating system for all other Macs, Wednesday's release is "for 13" Macbook Pro with Retina Display, 21.5" iMac (Late 2012)Mac mini (Late 2012)."
A quick look at the release notes doesn't yield much in the way of new information, possibly pointing to issues the new 2012 units are facing with some features in 10.8.2. Of note is the update's compatibility with the 21.5-inch iMac, a model that has yet to be released, though the no mention was made of the 27-inch version.
From the release notes:
About OS X Mountain Lion 10.8.2 Update for 13"Macbook Pro with Retina Display, 21.5" iMac (Late 2012)Mac mini (Late 2012)
This update is recommended for all 13? MacBook Pro with Retina Display, 21.5" iMac (Late 2012) and Mac mini (Late 2012) systems.
It includes all features and updates from OS X Mountain Lion v10.8.2 plus system-specific enhancements and fixes for Late 2012 systems.
New features include:
- Single sign on for Facebook
- Facebook as an option when sharing links and photos
- Facebook friends' contact information and profile pictures in Contacts
- Facebook notifications in Notification Center
- Share scores to Facebook, Twitter, Mail, or Messages
- Facebook friends are included in Game Center friend recommendations
- Facebook Like button for games
- Challenge friends to beat your score or achievement
Other new features
- Power Nap support for MacBook Air (Late 2010)
- iMessages sent to your phone number now appear in Messages on your Mac
- From Safari and Mail on your Mac you can add passes to Passbook on your iPhone or iPod touch running iOS 6
- New shared Reminders lists
- FaceTime now receives calls sent to your phone number
- New sort options allow you to sort notes by title, the date you edited them, and when you created them
- Dictation now supports Mandarin, Cantonese, Spanish, Korean, Canadian English, Canadian French, and Italian
- The Dictionary application now includes a French definition dictionary
- Sina Weibo profile photos can now be added to Contacts
This update also includes general operating system fixes that improve the stability, compatibility and security of your Mac, including the following fixes:
- An option to discard the changes in the original document when choosing Save As
- Unsent drafts are opened automatically when launching Mail
- Receive Twitter notifications for mentions and replies from anyone
- URLs are shortened when sending tweets from Notification Center
- Notifications are disabled when AirPlay Mirroring is being used
- SSL support for Google searches from the Smart Search Field in Safari
- New preference to have Safari launch with previously open webpages
- Graphics performance and reliability enhancements
- USB 3 reliability enhancements
The update weighs in at 654.49MB and can be downloaded via the Mac App Store or Apple's Support Downloads webpage.