Will sound like sacrilege, but I returned one of my two non-yellow, quietly-running 27" i7 iMacs. I still have one at my secondary working location that requires the machine to be used relatively little, but my home iMac (also my prime work machine as I have a home studio) has now gone back to Apple. I received a full credit for it. A fine machine, but... Quite simply, the screen has proved to be way too much hard work for my eyes. The wall of light that irradiates one's face when sitting at a reading distance is overwhelming. Great for movies when sitting back at a comfortable distance, but for up-close work, it's like sitting with my face a few inches from a TV. Interestingly from my point of view, I never had this problem with my former 24" Apple LED display. I used it with a Macbook Pro and for whatever reason, viewing was entirely more comfortable. So, yesterday I went back to a (newly bought) 24" LED display and MBP combination. I regret having sold the earlier setup to get the iMac, but at least the MBP is a newer version than the one I had so it isn't a 100% step backwards. Having used this latest pairing, I am absolutely certain that this 24" LED display screen is doing something very differently to the iMac's screen. Whether it has to do with the size or the technology used, I have no idea, but I definitely feel much, much more comfortable with the 24". It's not that one is brighter than the other, but more a case of the 24" feeling less like the light is being "thrown" at you. Less "hot" on the eyes even at what appears to be the same brightness level. Anyway, it's enough of a difference to have made me spend more money rectifying it.