Sony is really keeping its promise on firmware updates. The latest one is already seeding to Xperia Z ultra users around the globe with some key improvements.
X-Reality for Mobile display engine included
Superior Auto mode included in camera settings
Enhancement of stock email
Improved battery life
Improved video playback
One-hand keyboard operation possible now
White background UI
All those features are sure to make the quite an improvement regarding user experience as far the early adopters have confirmed, If you haven't received the update don't panic as these updates take times, You might even have to wait for a few days for it to arrive on your handset. It will probably be best for you to check both over-the-air service as well as Sony's PC companion software though.