Just wanted to share my experience of this. I have a 2 year 6 month old MBP 2011 (AMD 6490M) here, which over the last couple of weeks started developing the same old graphics problems (blue/black lines, split-screen graphics etc etc). I tried the gfxCardStatus trick and moving/altering the 'kexts' from /Library/System/Extensions which worked for a while, but eventually had the same problems. I was left with a $3000 MBP which I could only use by booting into Safe Boot (thus losing the vast majority of features one uses on a portable computer).
Happily, I took it in to the Apple store yesterday and they agreed to replace the logic board for free (I do not have extended AppleCare). I was prepared to fight my corner with lots of evidence of this being a genuine hardware problem, but didn't need to (which makes me think they are coming round to the fact that this is a design flaw). I know others have reported that replacing the logic board does not work, but I am at least happy they have acknowledged that there is a problem (if it fails again, I figure I have ample evidence to request a further replacement).
My advice for other people wanting to try to get the most out of a trip to an Apple store in this case -
1) Book a genius bar appointment early in the morning - the staff are less tired/cranky after a full day of dealing with angry customers, so are more likely to be receptive.
2) Take a photograph of your Mac's symptoms with you (e.g. blue/black lines on screen in my case) - this way, if you can't replicate it in the store, you can show clearly what has been happening.
3) Back up your Mac - if you are fortunate enough to get a repair, you want to be able to get it done there and then, so have it backed up and ready to go.
4) Change your Mac password to something throwaway (just while it is in the store) - you will have to hand over the password when you give them the laptop, so you don't want to give away your main password (that you probably use for lots of other things...)
5) Gather all the details of your Mac's history - where you bought it, when, how much you paid. If you can get specs from the System Preferences about the GPU (e.g. if you have a 6490M etc), all the better.
6) Gather as much evidence of the general GPU problem as you can find. I made a document of dozens of links to articles referencing this problem, as well as this thread, the various Twitter accounts/feeds, the Facebook account and any other major sites that showed the GPU problem was not just on my Mac.
7) When you go to the Genius Bar - BE NICE (THIS IS THE MOST IMPORTANT TIP). Any design flaws are not their fault - being nice and civil will go much further than storming in screaming at people threatening class action suits. You can always use this as a last resort, but much better to start off on the right foot.
8) Do not be fobbed off when quoted a price for repair (they should be fixing this for free). Ask to speak to the manager/senior Genius Bar staff member, and explain that this is a design flaw (use the evidence you have gathered)
9) If all else fails, thank them and try to get their details before leaving. Then phone Apple customer relations and explain the situation again.
I hope this helps some of you and best of luck to all with this annoying problem.