I also thought the rendition of the world, both straight and magical, was refreshingly new. Chamber of Secrets suffered from repeating but not extending the fey atmosphere of Philosophers' Stone (I thought). This film gives us a damper, colder, more mutable world. The enigmatic standing stones reminded me of Spirited Away, in fact.
But, there is one question you will expect me to address. Sirius and Lupin - any romantic subtext? Hell, yes. I know I always say that but - well, you go and see it and judge for yourself. I thought it was delicately and charmingly done, without imposing on children in the audience.