After reading all the posts regarding the yellow tainted screens. I got my iMac fearing the worst. Upon first inspection the display seemed fine, but once I started it using it for a few hours I started to noticed the bottom right hand quarter of the screen was no way as white as the rest. Upon using the grey testing image, my screen actually does have minor yellow tinge. It's not really enough to put me off, but I can notice it. Then I thought to myself, is this problem brought on by heat? Are the CPU and GPU thermal spots causing discolouration to the display? Both are located near the bottom of the screen, and that seems to be where 90% of the problems are? Have Apple put enough shielding between the screen and components?