updated 01:36 pm EDT, Tue October 22, 2013
Free Mavericks downloadable via App Store
(Updated to reflect launch) Apple has revealed at its special event that OS X Mavericks, the latest incarnation of its Mac operating system, is free. The major update will be available to download later today at no charge via the App Store, with users of systems dating as far back as six years ago able to download and install the operating system.
Confirming details revealed during its beta, it can be used on the 2007 editions of the iMac and MacBook Pro, 2008 models of the Mac Pro, MacBook, and MacBook Air, the 2009 Mac Mini, along with all later versions of the devices. Craig Federighi also advised that it can be used on systems that are still running on Snow Leopard.
Mavericks introduces more than 200 changes and improvements to OS X, including enhanced multi-display support, interactive notifications from messages, FaceTime calls, or updates from websites; the iCloud Keychain, Finder Tags for organizing files, and Finder window consolidation in Finder Tabs. Compressed Memory, featured in the presentation, minimizes the amount of space inactive data takes in memory and frees up resources for other programs, while Timer Coalescing and App Nap help save energy and reduce power consumption. Access to iBooks, a new Maps app, and an updated Safari with Shared Links is also included in the update.
Update: Mavericks is now available through the Mac App Store in the US and Canada. Other countries should follow shortly. The upgrade is 5.29GB.