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Apple introduces Power Nap OS X feature that updates your Mac while it's sleeping

Apple just introduced a new OS X feature here at WWDC 2012 called Power Nap. It lets your Mac update email, notifications and photos in the background, as well as back itself up while charging. Whether or not Apple ever drops the word "Ultrabooks" (and trust us, it won't), this addition is a clear retort to all those Windows-based ultraportables that promise to keep web-based apps up to date. In addition to the new MacBook Pros announced today, the feature will work with the second-generation Air, which makes us think all other legacy Macs might be excluded. Supposedly, too, the technology goes easy on the battery and won't stir up the fans, though Apple claims they're quieter on the new Macs anyway.

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Myriam Joire contributed to this report.