In dec of last year I picked up a 21.5" 2013 iMac and have been using it daily since. Love it for the most part...but there is one thing I have noticed that is a bit off. When it is an all black screen the backlights in the bottom right and left(stronger in the left) become really apparent. It's not an extreme issue as I don't really notice it unless I am looking for it and since im usually at 50-75 percent brightness its barely noticeable. Has anyone else had this issue though? I know the 27" displays are prone to issues but I thought the 21.5 were supposed to be rock solid I may see if they will replace it, not sure.