Bloglink overview firmware update: http://xperiazreviews.tumblr.com/post/50665345293/sony-xperia-z-firmware-update-may-17-2013
– NFC Tags upgrade
– Performance enhancements
– More Vibrant display with deeper blacks and greater colours
– Bug fixed with 12mp option to 13mp option in camera
– White balance display calibration,
– Soft keys and nav bar changed to black (instead of grey)
– An option to disable the notification light
– Small apps icon changed.
– Edit name tag in gallery
– White balance
– World time clock widget
– Tool widget redesigned
– Black task bar
– Camera launch slightly faster compare to my wife on the previous version
– Pulse notification light
– Stamina mode led fix with explaination of stamina mode
– International keyboard look different as well.
– Better App functionality
– Image processing algorithms have been greatly toned down.
(All these Upgrades were found on several blogs online)