OS X Mavericks Features
Many of the OS X Mavericks features are aimed at power users, some of the feature highlights include:
Finder has tabs support with drag and drop, window merging, and full-screen support
Tags come to the Mac for searching meta data, tags show up in the sidebar
Multi-display enhancements: support for full screen, menus span multiple displays, Docks can be summoned from any display, spaces span independently across multiple monitors
Significant performance improvements, including compressed memory, AppNap, Timer Coalescing, OpenGL 4, accelerated smoothed scrolling
AppNap suspends and resumes background apps and processes on the fly
Safari 7 includes major under-the-hood improvements, and includes a social stream and link sharing feature that watches your social networks for interesting links
iCloud keychain keeps track of all passwords and logins, stores them encrypted in iCloud and remembers all logins, Safari will auto-suggest ultra strong passwords
Notification Center improvements, you can now respond directly to Notifications from the Notification Center without launching the specific apps, and iOS push notifications will arrive in OS X, they will also show up on the lock screen of OS X
Apps automatically update in the background
Skeumorphic interfaces are gone, missing from apps, from Calendar, Reminders, etc
Calendar improvements provides suggestions, weather updates for location, travel expectations for time to arrival, and much more
Maps come to OS X, can send directions from Mac Maps to iOS Maps
iBooks arrives on OS X as a book reader, syncs with iOS devices, allows note annotation, includes built-in study cards based on notes

The OS X v10.9 Developer Preview supports the following Macs:
- iMac (Mid-2007 or later)
- MacBook (13-inch Aluminum, Late 2008), (13-inch, Early 2009 or later)
- MacBook Pro (13-inch, Mid-2009 or later), (15-inch, Mid/Late 2007 or later), (17-inch, Late 2007 or later)
- MacBook Air (Late 2008 or later)
- Mac Mini (Early 2009 or later)
- Mac Pro (Early 2008 or later)
- Xserve (Early 2009)

OS X Mavericks Developer Preview 4
This is a pre-release version of OS X Mavericks. To get OS X v10.9 Developer Preview 5, download Developer Preview 4 from the Mac App Store, then use Software Update to install OS X v10.9 Developer Preview 5.