There are many documented cases of a high pitched noise (or whine) when you lower the screen brightness on the last two iMac iterations (2009 and 2010 model). It seemed to affect all 2009 - 2010 iMacs. The noise is like a very high pitched dog whistle. I went through 4 iMacs and ended up getting a refund in 2009 - despite loving the iMac very much - I just couldn't stand the noise - which only went away when the iMac was in full brightness. If the noise is away I'd be more than happy to buy one. I was wondering if those who noticed the problems with the 2009/2010 iMacs would be willing to post their experiences of the new 2011 model? Thanks in advance.