A new feature in this version of Android include multiple user support. Multiple user accounts can be added (each with a separate Google account), where each user has their own application data and settings. Other features include Gesture Typing (which is rather awkward on a 7 inch tablet) and lockscreen widgets which raise a few security questions. Of course there are the usual performance enhancements and bug fixes.
The update is gradually becoming available to users around the world and is 80.6 MB in size.
KitGuru says: One of the joys of Nexus devices, my Samsung Galaxy S III won't see this update for a few months.