I just read an excellent article about HP, and it says basically everything I'd say on the topic. Probably better than I would. I'll throw a few sentences below, otherwise I highly recommend the entire article, here.
I've even heard some Christian parents express delight that the HarryPowered by ScribeFire.
Potter novels have sparked reading interest in their hitherto
literarily indifferent offspring - the implication being that content
doesn't matter as long as kids are reading something. Could a similar
case be made for reading pornography?
In the context of occult literature and cinema, Harry Potter is
relatively soft-core, but its sanitized portrayal of the black arts
arguably makes it more potently subversive. Interest in the occult
incited by getting caught up in the Harry Potter phenomenon is likely
to carry over into deeper exploration.