One of OS X Mavericks’ premier features is the ability to use different full-screen apps on different displays in a multi-monitor setup. The enhancement over previous versions of OS X also allows the Mac Dock, Mission Control, and Menu Bar functions to be accessed on each individual monitor…
YouTube user MrThaiBox123 filmed a video of the new functionality in a setup with six monitors (via @DetroitBORG). The narrator discusses some of the pros and cons of the new feature, and the video is worth a view for anyone interested in the new capabilities.
Keep in mind that OS X 10.9 is currently in its first developer preview, so any of the issues described in the video above could be rectified by the fall release date.
In addition to the above feature, Mavericks also includes improved Finder functionality, Maps and iBooks apps, and various performance improvements.