I have the greyish smudge too on the iMac I bought in 2011. Found this problem this year, but I cannot tell when it appeared. Of course my Apple Care was out of date. Just went to the Apple store for a frustrating experience. They "Apparently" do not know about this problem... even never heard of it... well I found that page... well those 84 pages today! That's a lot of people that share the same problem! They wanted me to pay 500$ for a new scren.
Well. I do think that...
-This problem is caused by a manufacturing problem. (it's not grease under the window.)
-I am not the person who is manufacturing these computers.
-A screen that last for only 3 year is not a good screen in my own opinion.
"Now Mr Jobs on your cloud in the sky... I have a question for you: "Would you be a happy customer if you had bought a computer that cost more than usual computers, because you beleived in the product and after 3 years the screen is broken? Would you reconsider what you think of the company who sold you this computer?"
-I think I have paid enough when I bought the computer.
-This is not what I was thinking about the sturdyness of Apple computers. I had an excllent experience with a previous iMac that was no longer supported.
-This is not the experience Apple sold me, in their advertisements... and it's not the HD that they've promised me.
-The guy at the Apple Store told me: "You know, it's electronic... it breaks!" Ok, so why is there other machines same as mine that don't have this screen problem? And by saying this I can now ask myself if Apple is applying some planned obsolesence to its products... just asking.
-Apple care... ok Apple care. A beautiful name for a prolongated insurance... when I go to Apple, I do not want to have the same buying experience as if I go to Future Shop. And if the screen is doomed, i'm not the entity who built it defective.
-As a customer, I do feel I'm being let down by the company who made these computers.
-After my visit to the Apple Store... No one could even tell me what happened to my screen... however, there was one thing sure... I had to replace it for 500$.
-Yes, I do think I've bought a lemon.
-Yes, I will telle this story to my friends and relations... they will surely be more comrenhensive.