One of the main features of OS X 10.9 Mavericks that was demonstrated at WWDC 2013 is the ability for the new OS to use full-screen apps on different displays while in a multi-monitor set up. The mode 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.
Of course, we are morally obligated to remind you that OS X 10.9 Mavericks is only in its first developer preview, and things could change drastically by the time it is officially released to the public.