The early reviews of this film are all over the place, so I was a little concerned going in. My opinion in a nutshell: wow, that's exactly the mood and spin on the story I wanted to see. I liked it - a lot.
A child is born. Yet it is not the child who is the destined one now in danger, it is the grown prince who the usurper now no longer needs. Right away, the paint-by-number convention of the hero's journey has a twist. It's not a huge twist, but it underscores how completely interchangable most hero stories are that a single footstep off the path feels like a major difference. And that's a common theme of the film: it's all conventional, but just ever-so-slightly out of phase with the archetypical moments giving it a surpsing fresh feel.
One of "cringe" moments of LWW was how quickly and completely the four reverted back to being children they had been despite half-a-life spent in Narnia. In Prince Caspian, one of the themes is to address this, rotating in the opposite direction: the children are not coping well with being just children again. They were kings and queens with more life experience in Narnia than in the "real" world and they have had a hard time in the year which has passed, making the transition back.
The four children do not enter the story on page 1 ... they are almost an accidental addition to a story which is not their own (even more so than in the novel). Yet they do not realize that the world does not revolve around them and their desires to play the saviour role even at the cost of Caspian is a subtle layer of compexity I found that facinating. Hints of complexity are everywhere. The good side are not all good - the idealism for the old days has become a bit twisted and embittered. The evil side is mostly not evil - the villain is constantly fighting to keep his own side motivated to fight (with a subtle complexity that the harder the kids fight, the more harm they do, simply uniting their enemies against them). Old enemies are now allies ... and the "temptation to summon forth the witch" scene is very, very well done and very, very well resolved when it happens.
There is a really interesting mix of moods here. Many reviewers found the opening hour dull, but to me that's where the real strength of the movie exists - the wonder, the conflict been darkness and idealism, the facinating way the kids become more comfortable with being just children as their old skills and strength are remembered. I love the acting and characterization ... Peter has an aura of expected authority, Edmund is portrayed as having deeply matured with his experiences, Susan is a truly terrifying presence on the battlefield, while young Lucy is much more at ease, much less awkward in her youthful movements than in the first film. There are some very, very dark and bleak scenes and some wonderfully light and beautiful moments.
There are a couple of missteps. There's an awkward dream sequence that I didn't think worked. I think that the characters, for the sake of getting in some big battles, turn a blind eye to the fact that rank-and-file soldiers are not evil. Conversely, there's a scene or two worth of reconcilliation at the end which I think are missing. There were also a few lines that reminded me that this is a writer who liked to backstab the non-religious audience with patronizing theology.
However, on the whole, with a little imagination to bridge the ommissions, I found this to be a surprisingly mature world hidden within a traditional fantasy. Well worth the evening.