Apple has pushed an update to their next-gen OS X, Mountain Lion, where the Developer Preview 3 release has been updated from build number 12A178q to 12A193i. Apple says:

If you already have Mountain Lion Developer Preview 3 installed, choose Software Update from the Apple menu to download the update from the Mac App Store. Download Xcode 4.4 Developer Preview 4 from the Mac Dev Center to continue building apps for Mountain Lion Developer Preview 3 Update.

9to5Mac notes a change with the new update, where they've spotted a "Do Not Disturb" setting in Mountain Lion's Notifications Center:

Apple has baked in a fair amount of iOS-like features, such as Reminders, Messages and Game Center. Mountain Lion should roar its way onto your Mac sometime in late summer 2012.