The 793MB update not only includes Android 4.3, it also includes a new home launcher, similar to the one on the Sony Xperia Z1. The update adds the Sony Smart Social camera, support for "Xperia Theme" and a new battery stamina mode. The latter allows you to increase the standby time of the battery by an incredible 400%. The update also supports the launch of multiple small apps and brings restricted profiles for multiple users.
The app shortcut on the top left of the screen has been removed by the update, possibly the only downside to the whole thing.
Android 4.3 has arrived for the Wi-Fi version of the Sony Xperia Tablet Z
source: XperiaBlog via AndroidAuthority