Just opened a new 21.5" iMac.
Turned it on and a white screen popped up 1st thing.
The bottom looked all yellowish like it was cigerette stained yellow.
Very very noticable.
The guy on the phone said they would exchange it and it should not have any yellow.
"If you stand up and run in place for 5min, then you drink 3 shots of Mountain Dew, then spin around in your chair 17 times, put up an all white (or grey) wallpaper, set the screen to max brightness, place your head 5 inches from the screen, stare without blinking for 120seconds, then sit normal and look at your screen, you will notice a yellow tinge."
I've had two i7 iMacs before the one I have now, but none of them had a noticeable yellow tinge as far as I can tell. So I don't want to say the issue is completely solved, but I do think it has gotten better.
All three models are from the Czech Republic factory.
So if the iPhone 4 yellow spot issues are caused by the evaporation process not being complete, how does this reflect, if at all, for yellow iMac screens?