Share your experience!
The 4.4 KitKat just came on my Xperia Z1. Should I update or wait for the problems to be fixed?
It is your choice,you may not encounter any issues.Read more here:
http://talk.sonymobile.com/t5/Xperia-Z1-Z1s/Z1-Z1s-4-4-2-update-issues/m-p/607929#U607929
Just updated to 4.4, it's working fine and also I turned on the water tap and positioned it on the back of my Xperia Z1 just incase it heats up 
Do not put water on your device if it is very hot,it could damage the device.
An other test subject for Sony , you should have waited. This update is by far the worst for this phone.
Probably you are the only one claiming no issues at all, mine lags pretty bad and i noticed a bug with the camera while taking pics off the button when screen locked.
What's the point of waterproof if I can't put water on it while it's hot?
I had no issues at all.