I know there are several posts re this on the forum, but I can't find an answer to this. I just bought a 2011 21.5" iMac. Its fantastic. But after a few days of using it I've noticed that the bottom of the screen has a very slight yellow tint. Can notice it if I move a safari window around the screen. My question is, does it get worse? I can live with it as it is, but if it is likely to gradually get worse then is it worth swapping? I've looked at a few models in a shop and some seem to have worse screen defects than this, whereas others seem fine. So just wondering how stable the screen is likely to be from now?