Just to let you know, I sent three back due to the gradient and yellowing issues - I was talked into a 4th replacement instead of a refund (to be fair, I think I could have just kept sending them back forever - apple couldn't have been more helpful) and I'm glad I was - No4 has a great screen, no freezing (and it was delivered before the fix) with no dead pixels - a very happy iMac owner now. Good luck with your replacement.
That´s good news. I am also awaiting a replacement unit. The one I am typing this one arrived last friday and isn´t capable of portraying real white on 80% of the screen. The one before that had severe backlight bleeding and gradient issues. What´s the production week of your fine machine?
Thanks,
Lance