According to Apple, Mavericks has a dual focus. Its first and most important goal is to extend battery life and improve responsiveness. Secondarily, Mavericks aims to add functionality that will appeal to "power users" (Apple's words), a group that may be feeling neglected after enduring two releases of OS X playing iOS dress-up.
Is that enough for Mavericks to live up to its major-release version number and to kick off the next phase of OS X's life? Let's find out.