The update, titled "MacBook Pro Retina SMC Update," comes on the heels of a Thursday firmware release which brought the same functionality to mid-2011 MacBook Airs.
As MacRumors reports, the system management controller (SMC) update enables the new Power Nap feature that comes with Mountain Lion.
Limited to newer MacBook Air models and the MacBook Pro with Retina display, Power Nap keeps Macs up to date and allows for the automatic backup of data while the machine is sleeping. The automatic data-refreshing service, which handles Time Machine and iCloud syncing, is both silent and power-efficient.
From the release notes:
This update fixes several sleep/wake issues to improve the stability of MacBook Pro with Retina display (Mid 2012) computers and is recommended for all users running OS X v10.7.4. It also enables Power Nap support for users running OS X v10.8 or later.
The update can be found in the Mac App Strore while settings for Power Nap reside in the Energy Saver pane of System Preferences.