Achtung! This post is full of spoilage. It assumes you've read the books and seen the film. If you don't want either spoiled, go away!
I was neither disappointed nor blown away.
The film begins with a somewhat awkward prologue explaining the whole parallel worlds slash dust slash daemons slash Magesterium thing. When it started, I was somewhat upset, because I felt it explained too much up front instead of letting us discover these things as the film proceeds. Having finished the film, I still feel this way, but I understand better why they chose to do it.
As with all epic novel series film adaptation, important stuff finds its way to the cutting room floor. (As if cutting rooms exist anymore - everyone does digital intermediates now.) The books are really for young adults, not children. And the filmmakers decided to make the film adaptation suitable for a younger audience. A lot of the subtleties of the novel have to be made ... less subtle.
One example of this loss of subtlety is the handing of the alethiometer. In the books, the aletheometer points to symbols in succession or multiple times to indicate varying levels of meaning. Lyra interprets these symbols intuitively; there are no visions or hallucinations. But because this concept of layered meaning can be difficult for younger people to grasp, the filmmakers shorthand the whole process with visions. It is a shortcut that makes sense from a cinematic perspective, but I felt that the vision sequences weakened the emotional impact of Lyra's ability.
Lots of things were done to make the film more accessible to a younger audience. In the novels, touching another person's daemon with your bare hands is the moral equivalent of rape; when it happens to Lyra at Bolvangar, she merely passes out, as though it were simply painful.
The ending, I have read, was reworked to end where it does, instead of at the end of the first book. At the end of the first book, Lord Asriel cuts away Roger's daemon (killing him) in order to tear a hole into a parallel world. Not at all a happy, family-friendly, holiday movie ending.
All of these changes, individually, are understandable. But together, they noticeably lessen the horror and moral outrage we are supposed to feel over the Magisterium and intercission. The movie reads like a naive, headstrong girl on a fun adventure with bears, witches, and bad guys.
All that said, there was a hell of a lot to like. For those who know what's going on, most of the important stuff is there. (Sometimes, though, it did feel like Lyra had read the book before-hand. E.g., when Lyra figures out that the Oblation Board is cutting away daemons.) They haven't really changed the message; they've just fiddled with the way in which it is presented.
It is visually scrumptious. I very much want a jet zeppelin now. There are some lovely set pieces, and the Lyra/Iorek relationship is developed very nicely. Only occasionally did the effects look effect-y. The focus puller, though, needs to be fired. Lots of buzzes and near misses. More than in any other film I've seen recently. The music was ho-hum, and the Kate Bush song during the credits was utter yuck. Obtuse lyrics, bland melody. Won't be winning Best Song.
Dakota Blue Richards does an outstanding job. She was a great find. Nicole Kidman wasn't bad, either. I had been expecting her to be a bit overblown.
So if you enjoyed the books, go see the film. It will not offend you much. If you haven't read the books, go see the film. But you might leave feeling like you're not entirely sure what's going on.