I had 2 x new MAc Pro's about 3 months ago when they first came out. Spent over £2.5k and had an issue where there was a shed load of white flickering on my screen.
Tested with different monitors and still the same. I said to Apple must be a GPU issue, they tried helping me for about 24 hours then just decided to bury their heads in the sand as it appeared to me they had no idea how to fix it.
Rather than be understanding of my frustrations, they simply said that it must be my monitor (which it wasn't as tested with others) and that I'd either have to put up with it or get a refund.
In the end I stuck two fingers up to Apple and built my own top end PC instead.
Glad I have slung my Apple tinted glasses and I must be honest, I have had a faulty Macbook Pro, black older Macbook as well as a new Unibody Macbook.
Perhaps its just my bad luck or the circles I frequent but I know lots of people that have had Apple hardware issues and for all the positives of owning a Mac, I do think reliability is something of an achilies heel for Apple.
I wish I could be more positive with the OP's issue, but having got zero help from Apple, I wouldn't hold your breath...