I just got a late 2009 21.5" iMac to upgrade my 2008 20".(Not a huge jump but I got a good enough deal so I went for it anyway) Been trying to use it for a few days, but the screen is so hard to look at. I thought at first it was the brightness, so I turned it down. Still the same. Can't be the LED backlight because I use a MacBook with LED backlight almost every day and crank the brightness up fine. If I put my 2008 iMac next to it and turn up the brightness it's perfectly fine. I am the exact same distance from the screen as before, and have tried moving back, no change. One thing I have noticed is that the screen of the 2009 iMac is a lot cooler and shows whites more. However even when on the desktop or playing games it gives me a headache. When I switch back to the 2008, I feel fine. I may end up returning it because of this. Just wanted to hear some feedback on why this could be.