I don't enjoy much the WOT books written by Sanderson personally, but associating them with "fan fiction" is wrong-headed and plain stupid. The fact Sanderson is a fan himself is a plus, it's obvious he has the greatest respect for RJ's work and RJ's intentions, not to mention he's working with RJ's editor and RJ's support team. He's also been a model of generosity, selflessness and openness through the whole process.

The books were released too fast, and there's all sort of little things that are OK for many readers and undermining the reading experience for others, and IMO so far Sanderson/Harriet have made one or two really bad calls (mostly by deciding to publish TGS instead of postponing the release to give Brandon time to finish the four storylines up to TG. 75% of the problems with TGS/TOM have arisen from not doing that, IMO).

But none of that make the books "fan fiction". FF is written by amateurs stealing a setting and characters from a writer for their own "creation", and not in any way concerned with respecting the original work. The Sanderson books are giving us RJ's story in a form that would not have been RJ's, but it's still for the most part what RJ intended for AMOL (not in the right order, and with story holes filled by Sanderson using the notes when he could and his imagination when he was forced to).