While we haven't seen the changelog, looking at screenshots from a post-updated Sony Xperia Tablet Z, Sony has moved the notifications bar to the top of the screen and had also centered the virtual buttons. A pull-down quick settings feature is now available, similar to what is on the Xperia smartphone lineup.
Running down the rest of the specs to refresh your memory, the Sony Xperia Tablet Z is equipped with a 10.1 inch display with a 1920 X 1200 resolution. This works out to a pixel density of 224ppi. Under the hood is a quad-core 1.5GHz Qualcomm Snapdragon S4 Pro processor with the Adreno 320 GPU inside. The slab has 2GB of RAM aboard and 16GB of native storage onboard. Of that latter figure, only 11.6GB is available for use by the tablet's user, although a 64GB capacity microSD slot can be employed. The back-facing and front-facing cameras weigh in at 8.1MP and 2.2MP respectively, and a hefty 6000mAh cell powers the slab. With an IP certification of 57, the tablet is both waterproof and dustproof.
source: XperiaBlog via MobileSyrup