The casting was perfect. The girl they found to play Lyra inhabited the character just right, and I pictured Mrs. Coulter as Nicole Kidman even as I was reading the book. Probably the best surprise was Sam Elliot as Lee Scorsby. I also think they did an excellent job with the daemons, Pan in particular. The bears were also well-done, although I was a little less impressed with them -- I liked how their speech had the feel of roaring, but the mouth movements were pretty far off. They did move like bears, though, and overall the film was stunning visually -- beautifully realized steampunk elements like the airships, the way that daemons exploded into Dust when their people died, Lyra reading the Compass. It's one of the most appealing films just to sit and watch that I've seen in a long time.
So, as always after watching a movie based on a book, now I'm feeling the need to read the books again... As if I didn't have enough to read already!