Apple rolled-out an update for the 2011 and 2012 MacBook Air notebooks shortly after the release of Mountain Lion that added the Power Nap feature. At the time the update was rolling out to the MBAs, Apple was promising the same for the MacBook Pro with Retina Display. The update for the Retina display MBPs was noted as coming soon, and well, it looks like Apple has lived up to that soon timeline. As of now, those sporting a MacBook Pro with Retina display have the Power Nap update ready and waiting. The update arrives as an SMC update by way of Software Update and once you have this installed — your Mac will be able to stay up to date even when it is in sleep mode.