I think she's a good writer. I don't think she's a perfect writer, but I have a hard time thinking of any book I've read where I didn't have any questions or criticisms.

She tells a good story, and she makes me laugh and cry when I read her books.

A lot of the JKR isn't a good writer talk (along with a fair amount of the Joss Whedon is so shitty talk) seems to come from a disengenous place to me. I can't tell if it's an "I used to like this stuff when I was a kiddo and now I have outgrown it and therefore must act like it is beneath me" or genre snobbishness or what.