I'm not a huge fan of the books by J.K. Rowling. I've read them, but only to see what all the hubbub is about. They're good writing, but better fantasy writers exist and it feels as if all the concepts have been used before in other sources. I did like the decidedly adult turn the series took around book four.
That being said, the trailer looks epic. It shows Harry fighting for his life against Voldemort and definitely has a more adult feel to it than the earlier films. Among other things, the 'Harry Potter' franchise is about growing up and it looks like the cast and creators have done just that. Judge for yourself.