The last thread on this has been inactive for a while so I decided to start a new one. When I turn down the brightness on my 27" iMac, you start to hear a kind of electrical buzz. It gets pretty loud at low brightness settings. I noticed that when the computer is cooler (i.e. after booting up for the first time) the sound is not as loud as when it gets hotter. The thing is, I'm not sure whether or not I should return it - will this problem get worse over time? I'm not really affected by it since I use the system on maximum brightness all the time anyways. Any opinions? Note that this is iMac #3. First two devices had stuck pixels. Yep, Apple QC sucks. Thanks!