we had an Xperia S...
... with the slight yellow-tinted screen.
As soon as I noticed, I took it back to the store and the screen was replaced. Under warranty.
Another Xperia had a power supply / battery discharge issue and was fixed - under warranty. 2 different issues, supported by Sony and the shop. Also, all the Android updates for the Z series have been fairly timely. 9not as fast as some, granted...)
Biting the hand that feeds IT
