Apple's Craig Federighi is up on stage talking about OS X Mavericks and he says the new OS, expected to come later this month, will add an hour of battery on existing MacBook Airs. There are also a number of new features coming to Mavericks like iCloud Keychain, Maps, iBooks as well as updated versions of native apps like Safari. Mavericks will be available today for free.
Notifications are also integrated into Mavericks so it is easy to manage Messages better.
Aside from performance enhancements, OS X Mavericks will be about new technologies, features and apps which determine the entire ecosystem.