Things they got right:
a. the mice
b. Trumpkin (even if they didn't freaking use his name)
c. the single combat
d. the ending
Overall the film was very much a disappointment, especially after how faithful and well-done The Lion, the Witch, and the Wardrobe was. There were a few changes I did approve of; I liked that Glozelle and Sopespian actually didn't like Miraz instead of just being greedy bastards, I could hardly argue with a bigger role for Queen Prunaprismia, and I totally loved how they collapsed the ground under the Telmarines. Oh, and the subtle Princess Bride reference was pretty sweet (and looking at the IMDb page, there's a Lord Montoya listed). And it was obviously important to change the order around somewhat so the tension could be kept up.
Honestly, most of the actual changes would have been okay. It's just that there were so many of them. And some of the most glaring ones were at the beginning. I hated that instead of a diplomatic but naive kid with some common sense like in the book, Caspian was more of a grown-up idiot. And WTF with Trumpkin automatically recognizing Susan's horn and everyone assuming it would bring the old kings and queens? The worst change, in my opinion, was having the White Witch show up. Yes, I adore her. But she's DEAD. They say they're going to summon her in the book, but they never actually do, and I suspect that even if they hadn't been killed first, they wouldn't have succeeded. Because she's DEAD.
Bleah. I could go on, but I don't feel like it! So there.
also: the only thing that irritated me about the books was that the the lion witch and wardrobe was a totally different narnia than the rest of the books. if they keep all of them just like the books, they're going to confuse the hell out of a lot of people.
What, you mean time-wise? Actually, that's a part they didn't change (but it's so utterly vital to the plot that I didn't count it--they also didn't change who the main characters are!). All of the books take place during slightly different times, except of course for The Horse and his Boy, which takes place during TLTWaTW.
I don't think any of the changes succeeded in making the movie less confusing. I thought the movie was pretty confusing and it could only have been worse for someone who hasn't read the books. Case in point, during the final battle Peter calls for a retreat, shouting "Back to the How!" At first my family and I all thought he was saying "Back to the house," which didn't make sense. Then I remembered that their base is known as Aslan's How and explained that to the rest. But no one in the movie had used that name before that point. That just made it needlessly confusing.