We use two 27inch iMac here, both bought in October 2010, same model, Quad-Core iMac, and one with dirty patches on screen that makes it unable to provide the expected service: edit pictures with Photoshop and LightRoom. I do fashion/beauty photography (HairShooter) and need a good workstation to edit photography. A franch team created a web-site dedicated to screen problems on Mac computers, dirty-screen.com, that Apple tried to shutdown months ago threatening to sue them. They are back and alive, legally backed, and fighting to have all of our Mac screens correctly fixed by Apple. It’s incredibly outrageous to buy a 2000$ desktop computer, targeted at power-user, and moreover graphists, photographers, web designers, that have screen problems only 1 year or 2 years after being sold, and being totally unable to display correctly a picture or photography! Please Apple, fix this problem!