These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Fandom Rivalry: A little with Harry Potter; inevitable given the two series' similar premises and that popular things will always be compared to everything. Earthsea fans feel that it was popularity-snubbed in favor of the (to them) more poorly-written/unliterary Potter. It doesn't help that Le Guin herself has criticized the series.
Most of her venom seems reserved for clueless reporters who don't realize how much Rowling adapted/borrowed from old fantasies (including this one)... Quoth Le Guin, "I read a review that called the Harry Potter Books a great, original work. I agree with the first part."
Flat Character: Aspen seems to exist simply to be there so Tehanu can have more in-universe feminist themes and a driving antagonist. As a character, it doesn't seem he has any real motives for completely hating women at all.
Aspen's motivations was clear enough: he was a follower of Cob and jealous of Ogion's trust in Tenar. He used Earthsea's common prejudices against witches (that had been established as far back as the first book) as one of multiple methods by which to attack her, and by extension Ged, and undermine their authority.
Ho Yay: Arren's introduction to Ged in The Farthest Shore. Look inside the text, you know it to be true. There's also a little bit between Ged and Vetch in A Wizard of Earthsea.
Seasonal Rot: A common fan response to Tehanu and subsequent books. The Other Wind probably attracts the most criticism for the revelation that the afterlife featured in the original trilogy was actually created by the wizards and blocks human souls from a blissful reincarnation. People who admired the bleak and austere character of the "Dry Land" tended to feel that this robbed the world of Earthsea of its poignancy.
Writer on Board: Le Guin was always a feminist, but between writing the third and fourth books of the series, she came to view many of the classic fantasy tropes she'd used in the original trilogy as sexist. The fourth book, Tehanu, has a drastically different tone and perspective, and many readers ended up feeling like they were being told they were wrong and stupid for having liked the earlier books. The fifth book, The Other Wind, follows up on the themes from Tehanu but strikes most readers as markedly less preachy.