I am indeed a Harry Potter fan. I have all the books (this makes my third First Edition too) and I think the stories are rollicking good yarns. I also have the movies (so far) on DVD.
Contrary to some of the things I've read, adult Harry Potter fans are not a bunch of TV-watchers who can't read anything more demanding than a comic strip. I read extensively, an eclectic mix of fiction and non-fiction. As a child, I read almost all the "classics" as I was a precocious reader and had a reading age well above my chronological one.
I think J.K. Rowling's books can be enjoyed by both children and adults because they can be read on different levels - just as you don't have to be an "expert" on art to enjoy the Mona Lisa or Michaelangelo's David.
I think anything that encourages people (especially children) to read more is a good thing. Surely books that entertain and give pleasure to millions should be praised rather than slated. We can get too precious about what constitutes a good book - which is why the Yarn Harlot gets frustrated when her husband tells people she is a best -selling author. They're all admiration until they find out she writes about knitting. Apparently, this isn't "real" writing.