I just got back from watching The Voyage of the Dawn Treader. (Warning: This post has one minor spoiler. If you've read the book, though, you would already know this.) It was good; please watch it, for the reasons outlined in the previous post! I thought there were only two negative things about it: First, the extra "evil" force they added in to the story (which was totally necessary for the movie, I think; the original plot was plenty sufficient for a book, but it did need a little something as a movie) was sort of cheesily done. It came in the form of an ominous "green mist". O_o
Second, they named the island where this evil originates (the island was unnamed in the book) the "Dark Island", which I thought was also a little cheesy. Anytime a fantasy story contains something that begins with "the Dark", I think it's a little cheesy... the Dark One, the Dark Forest, the Dark Knight, etc. It was cool when the first few people did it, but it's becoming quite a cliche.
Other than these two things, however, the movie was really well-done. It stuck very close to the book -- much closer than Prince Caspian did! A lot of the events happened somewhat out of order, but I think it still stuck as close to the book as it could while still being a good movie.
Most importantly, (and especially most importantly to Christians!) the movie maintained the two most crucial parts of the book: the points that referenced to Christianity. The first was Eustace's description of how Aslan turned him back from a dragon to a boy (there's your spoiler), which a Christian would recognize, once they heard it, as an analogy of what happens when you become a Christian.
The second was when Aslan told Lucy and Edmund that he has another name in our world, and that they must learn him by that name; and that in fact, the entire reason he had sent them to Narnia was so that they might learn him a little there, in order to know him even better in our world. What is not said, but what the readers (or in this case viewers) are meant to figure out, is that his other name is JESUS.
Once again, please watch The Voyage of the Dawn Treader... and tell everyone you know to watch it, too!