I have to be quite honest, in that my experience with reading the books so many years ago, Prince Caspian was the weak book dealing with the main characters (I do not count Horse and his Boy or The Magician's Nephew in this... they are mere side stories to the main storyline. They are also books 5 and 6 in the old way of ordering the books. If you go to Borders, and look at my displays for Narnia, I have put the books in the order that I read them. ) So I thoroughly expect the next two movies (Silver Chair and Voyage of the Dawn Treader to be spectacular movies.
So my expectations for this movie were met, in that it wasn't the best book of the series, so it wouldn't have been the best movie (see also the HP series, where HP5 was the weakest book, so it has been, so far, the weakest movie). Overall, I give it a B-, which is in line with most critics. In fact, you can go to Yahoo! Movies and read most any critic's review, and they will, for once, be right.
Two things stuck out, one good, one bad. The bad first. Someone should have told the directors that it is not necessary to do slo-mo battle scenes for minutes on end. It became tedious and irritating. For me, battle scenes = potty breaks. But everyone loves them, so they have to be in each fantasy movie. BORING!!!
The wonderful part of the movie, and the only thing that keeps me from giving this a "Sea" (sorry, had to), was the Christian theme of faith and reliance upon God, instead of trying to do it yourself, which was better displayed in the film than even in the book. In this respect, the movie is better than the book, because the failings of Peter and Susan to not see Aslan, and further, the determination that Peter had to take back Narnia from Miraz (and the subsequent deaths that Peter was responsible for), all because he would not wait for Aslan to solve the problems in his own time. Of course, it was the lessons that Peter and Susan had to learn before going back to the real world. This theme alone makes the film worth seeing. I was very impressed with the ability to put such a worthy lesson in the middle of a contemporary movie.
I think that, in future fantasy films, people will start becoming tired of the endless battle scenes, and will yearn for fantasy without bloodshed. Of course, I'm dead wrong on this. There have been battle scenes in movies from Lawrence of Arabia to Star Wars to the upcoming Mummy movie, which I have no interest in seeing. This is why I have such a love for Anne McCaffrey's Pern books, or with the film The Neverending Story, because they can make wonderful fantasy works without having thousands die in battles (now most of which are CGI created ad nauseum.)
My opinion is, that if you haven't seen it yet, wait for it to come out on DVD and then rent it or whatever, so you can fast forward past the battle scenes, but pay attention to the themes of faith and responsibility, which makes it stand out as a children's movie.