—The Fox was voiced by Rupert Everett. I’ve found him to be very British, not Midlantic, but perhaps he was persuaded to dumb down for this role.
—I was not impressed by Liam Neeson’s performance as Aslan. His speech was not majestic enough for the character, I thought. Ditto with Father Christmas: the impression he gives in the book is that of someone surprisingly stern. [Some of the pictures of Father Christmas in our world make him look only funny and jolly. But now that the children actually stood looking at him they didn’t find it quite like that…They felt very glad, but also solemn.] Furthermore, I didn’t expect him to look like a Coca-Cola Santa, but I did think he’d look like St. Nicholas: where was his staff? 
—But I had no problem with Tilda Swinton’s portrayal of the White Witch. That role was ripe for scenery-chewing, but she conveyed the right degree of menace. I also thought she was well-costumed. I’m not sure of the era, but I think there was a time when royals and titled women did wear those stiff gowns that bypassed the bosom entirely and went right from shoulder to shoulder. At any rate, they looked like armor, and remember, centuries earlier, Jadis had been a queen who “poured out the blood of [her] armies like water”. That said, I’d always thought she was supposed to be ghastly white, not merely pale, but whatever.
—I also felt the lack of propaganda about Aslan before we actually meet him. It wouldn’t have taken more than 90 seconds to add the dialogue about Aslan being “not safe, but good”. There wasn’t enough of a sense that the Narnians really revere him for his own sake, not just because he’s prophesied to end winter and banish the Witch.
—It also would have helped if Aslan would have been shown going over battle plans with Peter and with the other alpha males, even if it was only a brief visual. Then it would have been clear that Peter was to be the general because Aslan said so. And I agree that Peter wasn’t shown as much of a swordsman. Sword or gun, if you’re going to draw a weapon, use it!
—I can understand the decision to ramp up the chase scenes, but I personally didn’t dig it. The river scene really wasn’t necessary; the hero scene is when Peter kills Fenris (I will not call him Maugrim ;)). And I honestly don’t know why the scene with Tumnus and Edmund was created. Maybe it’s just me, but I was always partial to the scene where Edmund is cold and wet and hungry en route to the WW’s castle, almost turns back, but then mutters, “When I’m King of Narnia, the first thing I shall do will be to make some decent roads.” I don’t know why, but that always struck me funny.
—And for that matter, a lot of the dialogue was missing, as other posters have noted. “Us lions,” “Must more die for Edmund?” “We might all try minding our own business,” “And whatever happens, never forget to wipe your sword.” (or was that in there?) And two exchanges that I particularly liked: first, when the dwarf says, “This is no thaw. This is spring…This is Aslan’s doing,” and the WW snaps, “If either of you mentions that name again, he shall instantly be killed.” So we can really see both her frustration and her grudge against Aslan. And second, when all four children go through the wardrobe and Edmund drops a dime on himself by mentioning the lamppost.
—That said, I thought the sacrifice scene was brilliantly done, as well as the battle scene. And two small touches that I liked were Jadis wearing Aslan’s mane into the battle, and the Professor going from mildly interested to sitting straight up and repeating, “The wardrobe?” And if you haven’t seen it yet, don’t leave the instant the credits start. 
Nitpick: Prince Rilian was in Silver Chair. The guy you’re thinking of was King Tirian.
