I'm not sure if you're a fan of HPMOR. I personally am, and I think that this parody would lose a lot of appeal were non-Canon potter not a Mary Sue.

I also don't read fan-fiction at all (this is the only fan-fiction I've ever read), but I definitely don't go around saying it's good fan-fiction. I go around saying it's a good read that makes me laugh and makes me think.