Apple issued a software update for OS X Mountain Lion Developer Preview 3 this evening. Apple released Developer Preview 3 to developers. The update brings the build number of Mountain Lion up to 12A193i (from 12A178q).
One change noted by 9to5Mac is the addition of a "Do Not Disturb" setting to Mountain Lion's Notifications Center: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.
Besides the Notification Center, Mountain Lion also borrows a number of other features from iOS, such as Reminders, Messages, and Game Center. Apple first previewed Mountain Lion back in February and promises deliver to customers in late summer 2012.
Article Link: Apple Issues Update to OS X Mountain Lion Developer Preview 3