After the LG Optimus G and the Verizon Galaxy Nexus, now it's the Sony Xperia Z turn to get the unofficial Android 4.4 KitKat ROM treatment. that's the first of the 2013 flagship crop to get a KitKat ROM, if we don't count the Nexus 5, of course.
It is a stable ROM and most everything seems to be working, but since the mod is based on AOSP, there's no root or recovery here yet. The only minor quibbles are that you have to reboot twice for the Calendar to start syncing, and hit the home button when choosing a mobile network manually. Hit the source link if you are interested in installing it on your Xperia Z.
source: OP (XDA-Devs)