While iOS 7 was expected to be the star
The latest version of OS X offers a number of understated improvements that will please power users. It will also please iPhone and iPad users, because many of the upgrades are basically all borrowed from or inspired by iOS products. The update will overhauls some core pieces of Apple software, starting with the very basics. Finder, for instance, will be getting some new browsing features, including tabs and tags, which should make surfing around your Mac a bit more like surfing the Web.
From there, the upgrades start to drift pretty hard into power user territory. Screen-happy graphic designers out there will be happy to hear that full screen app support will now be supported on multiple displays
The new OS includes a lot of behind-the-scenes tech improvements, including increased battery life, compressed memory and so-called timer coalescing. All of these improvements will mean that the system will run better?up to 1.5x faster than in Mountain Lion.
Related to the purely technical improvements comes a big update to the old password management app. It's called iCloud Keychain
Otherwise, features within the browser have been improved and expanded. The most exciting of these happen in the sidebar on the lefthand side of the browser. These features includes the read-it-later-style Reading List
Calendar and Maps
Here's that flat design you've been hearing about. The new Calendar and Maps apps
As you might've anticipated, Apple is porting its popular iBooks software
Does all this sound thrilling? Not really, but Apple's smart to reward its most faithful users with simple features they've been asking for.
If you're running OS X Snow Leopard or Lion, you'll probably see a big boost in performance and stability by upgrading to Mavericks. If you're using Mountain Lion or do all your browsing in Chrome, you probably don't need to spend the extra money on Mavericks which will be available to the public this fall. Unless you want to, of course. And Apple wants you to want to.