Loved it, Loved it, LOVED IT!!! Maybe even more than any of the previous LOTR movies.
If you are a fan of the books you'll be glad to know that for the most part it's very faithful to the book. I only have 1 or 2 VERY minor quibbles.
Riddles In The Dark is absolutely the way I always pictured it in my mind. I was honestly almost in tears after that scene because it was just so incredibly well done.
Spoilers for book fans ... don't read unless you want to do some "research" before you see the movie:
There is some stuff from the ROTK Appendix, namely Appendix A-III (Durin's Folk). It flows with the film great but I was surprised it was there. Since I hadn't read the Appendix for awhile I had to think for a minute, which was hard at about 1am.