The question I have is this: Why does one have to "outgrow" Harry? For that matter, why is any book considered YA if it has a child for a protagonist? Take His Dark Materials as another example. Sure, the heroes are twelve years old, but so what? Does that mean that adults can't read it? HDM is a retelling of Paradise Lost, and how many kids would get that bit? Not that kids can't read it and get something out of it without the hidden analogies, but HDM is not just a childrens' story, and neither is HP. They're good stories, yo, and not just for kids (in the case of HDM, I think a lot of it would fly over kids' heads).
I saw parents bringing their five-year-olds to see Prisoner of Azkaban. That was a scary film! Too scary for kids that age. And yeah, it's a case-by-case call, but I don't think there are many seven-year-olds that would be able to get through Order of the Phoenix, nor should a lot of them be allowed to. OoTP is as scary in some places as parts of Lovecraft or Poe.
I'm not saying kids shouldn't read these books. I just wish that people, including reviewers, would stop telling readers that they're something to outgrow. (the actual line in the text says, "It also gives Potterites who have outgrown Hogwarts a new school to attend. ").
It's insulting to me and, I would think, to the authors of the books. [/rant]