I'm not saying they won't replace it for you as I've never dealt with Apple. I'm just saying that it's very likely they will know that it wasn't faulty hardware to begin with.
It
was faulty hardware to begin with, though, that's the thing. It might not be everyday usage to run the thing at 100% GPU load, but that doesn't mean it's out-of-warranty usage (although overclocking would be).
In any case, I'd be very surprised if they didn't replace it without question - I've never had any major hassle with in-warranty servicing from Apple, and with the margins they make on their hardware, it's easier to just replace it and have a happy customer than waste the time arguing.