I collected my 4th replacement from the Apple Store in Glasgow today and it is completely different from the other three previous ones. Screen is uniform white and bright. There is absolutely no colour change on tilting the screen. And a weird thing - the back feels and looks different - it's more matt than the last three. I checked a good number of the display models and all were perfect white screens and had the matt back. It's build week 7 as were two of the other three and the DL (Foxconn) factory. So something is going on. If you have tinting problems - return them folks. Not right.