I admit I was disappointed because I found parts of the movie dragged. I’m not all that interested in battles (I tend to skip over the battle scenes when watching LOTR).
I couldn’t remember the plot of the book very well (indeed, I found I had confused it with The Silver Chair). Things I liked:
Susan got more face time and lines and turned out to be an interesting young woman. She mumbles, though, and so I missed some of her lines. I like that she kissed him and that she was such a integral part of the battle.
Peter showed more vulnerability in this one, which was nice. Also, he showed his hubris. (I always pitied poor Edmund–such a petty crime to cause all that angst in LW&W). His one on one with Miza was quite good.
Lucy cannot act, I’m afraid.
I love wherever they filmed this–it’s gorgeous! But it did remind me of [del]middle earth[/del] New Zealand.
I liked the humor in the story (much of it added, except for Reepacheep–he is great in both book and film).
I think my “eh-ness” has more to do with the non-traditional story arc than anything else. God knows I am tired of boy meets girl etc or boy faces Great Challenges and Overcomes Them All in battle despite desperate odds etc, but I have to admit I’ve come to expect those plot lines. But I do like that Aslan is not explained away, that he is left mysterious and therefore somewhat anxiety producing. I liked Prince Caspian–to me it doesn’t matter if he’s older than Susan et al–after all, as they say, they’re actually 1300 years older than he is. He did have a bit of Johnny Depp going on.
The masks on the battlefield–what on earth? I kept expecting one of them to yell, “avada kadavra!”
The Poseidon guy was lame, IMO. But my 10 year old loved it. I do need to remember that these films are targeted for that audience. Could it be that we are approaching a fatigue in the fantasy film genre? They are starting to all resemble one another–hell, the Tube scenes look like they could be Harry Potter films as well (that might be because the Tube looks much the same now as it did then, but I digress); lord knows the school uniforms haven’t changed! 
One last complaint: the gait of the centaurs–it looked like junior high CG. The black leader was cool, but even he walked and cantered like a stuttering donkey. wth?
Edmund is by far my favorite–he is quite good (the actor) and I like his character.