We hope this will provide holiday relief for many iMac owners: Apple just released a firmware update for the graphics chipsets in 27" iMac models, intended to fix display issues. Apple states this download
Updates the graphics firmware on ATI Radeon HD 4670 and 4850 graphics cards to address issues that may cause image corruption or display flickering.
This update is only needed for the 27" iMac models introduced in October.
This should hopefully fix the issues that many are facing with their new iMacs, including our own Josh Carr, who's had display issues with his 27" iMac. We'll let you know if this update fixes these issues for him.
This update is available through Software Update, or from Apple's Support Downloads page.