There's one conservative blogger, Bruce Charlton, who while not Orthodox is a great admirer of Fr Seraphim Rose and agrees with his views on nihilism and modernity. Interestingly, he also greatly admires the Harry Potter stories and considers them edifying (teaching virtues like honesty, loyalty, courage etc); he is also greatly disappointed by Rowling's forays into adult literature, considering her to have sold out to nihilism and the sexual revolution.
So I think even serious traditionalists can get different things from these stories. As many here know, I don't have much patience for "fundamentalism" or see anything very sinister in the references to magic in these books. If you take that attitude where you have to reject the whole because it contains some fiction, you would have to disagree with St Basil the Great and reject all of ancient pagan literature (or any literature other than explicitly Orthodox writings) because they include some things we don't believe in, like polytheism. I would be more worried about e.g. Philip Pullman, whose stories are explicitly anti-Christian. Harry Potter, on the other hand, does not contain anything explicitly anti-Christian and it promotes sound virtues.
That being said, I do prefer the world of Tolkien and Middle-Earth to the Harry Potter fantasies, or even to Lewis' fables. In Harry Potter, there is a clear distinction between the "ordinary" world where Harry Potter begins and the magical world he enters when he becomes a wizard, which make it harder to take the supernatural elements seriously. There is also something cold and mechanical about magic as portrayed in Potter and elsewhere; it is morally ambiguous, like science and technology. It can be used for good or evil, but anyone with the right training can cast a spell or use a magic object. In Middle-Earth, on the other hand, there is a distinction between good and evil supernatural effects. Someone who is supernaturally powerful but good will not be able to have the same effects as someone who is supernaturally powerful but evil. There are no morally ambiguous spells or magical tools (that I can recall anyway). The ethos in this respect seems closer to Orthodox ways of thinking: an evil man will not be able to use a holy relic for evil, for example.
I wonder what people here think of Tolkien and the Middle-Earth fantasies.