I had a mixed reaction. I liked parts of it, but overall, I felt it lacked the charm of the first movie.
After I saw the movie, I read the synopsis of the book. Apparently, in the book...
...Aslan is trying to lead the Pevensies to Caspian, when only Lucy can see him and the others don't believe her. The complication is that because they don't believe Lucy, they are unable to find and help Caspian.
In the movie, however, the Pevensies manage to find Caspian much sooner. The entire plot hinges on Lucy going to meet Aslan in a random spot in the woods for no apparent reason other than to test of her faith - she certainly doesn't do anything there other than talk to Aslan (by not going there sooner and proving her faith, other innocent creatures, who had nothing to do with her not going there, die). Once she does finally go there, Aslan just roars and before you can say "deus ex machina" the bad guys are defeated. This makes everything the Pevensies did prior to Lucy going to that random spot in the woods seem rather pointless. And why couldn't Aslan just go to his stone tablet, where everyone else was to begin with?
Religious allegory aside, I found that to be rather poor storytelling.
Then, there's this exchange:
Lucy: Why couldn't you just come roaring in and save us, like last time?
Aslan: Nothing ever happens the same way twice.
A) That's not an answer.
B) Except for a few details, everything does wind up happening the same way again. Aslan brings sleeping warriors back to life, and they rise up and defeat the bad guys.
For me, the most effective scene was the temptation of Caspian and Peter by the White Witch. Very unexpected, creepy and suspenseful. Tilda Swinton is great.
Eddy Izzard's Reepicheep was very funny, though I wished he had interacted with our main heroes a bit more.
Another surprise was how I found former-traitor Edmund to be the most likable Pevensie in this film. I liked his exchange with Miraz about his title. "It's King, actually. Just king...Peter is High King. It's confusing, I know..."
I also thought that the raid of Miraz's castle by the Narnians looked awesome, even though it was already a foregone conclusion that it would go poorly, since Lucy didn't approve of it.