I got the top end iMac late 2012 - everything maxed out. But still I experience lag when playing a youtube video on full screen. It happens for me no matter if the video is 1080p or 320px - so it seems to be youtube being extremely bad optimized. But again, even if badly optimized, a i7, 680mx imac with 32 gb of ram should be able to play youtube in fullscreen without lagging. anyone else experience this ? ANy tips on how to fix ?