The first notable update for KitKat has just been released across most of the major AOSP and Nexus channels. According to Google software engineer Conley Owens, the KRT16S build includes bugfixes for the original Nexus 7 and Nexus 7 2013 (WiFi and mobile versions), Nexus 4, and Nexus 10. The binaries have already been added to the Nexus repository.
Screenshot credit: Tron87, Nathan Sparrow
Google has also updated the factory images for the relevant Nexus devices.