I hated the last book, it was so cliché, even for a children's book. And the references to WWII was too much to bear. Also, I hated that the "evil" ones were pure evil, with no signs of empathy. Though, I had to read it, having read/watched the others, and to let noone spoil it for me. And, you know, it's water cooler gossip material.
I never found Harry Potter to be a kids book, just a book written with a 6-8th grade vocabulary and such in mind, much like most newspapers. I did find her writing ability to be amateurish until about the fourth book and the first half of the first just cliche and completely unbelieveable, I can't see how any family would treat a member like total shit for so long without child protective services stepping in at some point. The last book is easily the best, however her inexperience with writing and experience with pleasing crowds shows by how she writes herself out of every corner. Sure people do die but it's not like X has to die OR Superman comes out of the sky and uses his heat vision. It goes more to the tune of X gets to die then some crazy, but plausible, shit happens and they get to live. Or the whole retroactively making *SPOILERS* Snape into a good guy. When George Lucas tried to pull similiar shit people were pissed (see Han vs Greedo) or how Han claims that the Falcon can do that race in 12 parsecs which by many people is just claimed to be poor dialogue (which it is) where as other die hard fans cite a book that discusses the race further stating that he took the short, dangerous path as opposed to the long safe one. Overall not bad books, just incredibly over hyped IMO.
Yeah, the last book was weak compared to the 6th. It just felt like she took the easy way out when writing it, and didnt really bring any real, true "surprises" that would really blow a reader away.