I bought the 1st imac 27 on february which was a week 6, but i can notice that it has a yellow tinge on the bottom, after realizing this is an issue encounter by most of the users, I decided to ask for a replacement. My 2nd imac was a week 9, and fortunately the screen was perfect(i put it side by side with the week 6 to compare b4 returning it). But only realized later it has a faulty superdrive. So, with no choice i have to return it. Today i received the 3rd one a week 12. The superdrive is good, but the *#$& screen is even worst than the 1st. The whole $&#^ screen is yellow, the moment i turn it on i can easily notice. My conclusion is, there are perfect screens existing, but it depends on luck, and I don't understand why their product quality is fluctuating. Right now i am really doubted what to do next. Please advice.