Earlier this week the New York Times Fashion & Style section reported on some parents' dislike of the Junie B. Jones series: "Is Junie B. Jones Talking Trash?" I have seen similar articles in the past in other newspapers; none of them seems to deter sales of the popular books. For a good defense of the books, see Pam Coughlan's piece in The Edge of the Forest archives.
... Rowling’s imagination has changed the perception of an entire generation, and that is more than all but a handful of living authors, in any genre, have achieved in the past half-century.
Speaking of Harry, the Wall Street Journal looked at some Potter reviews over the years. The Journal doesn't put many articles online for free, but this one is.