Aint it cool site has reviewed a large chunk of the film and dont think much of Ben and the other child actors but likes Skandar's performance

Here's the review

For the most part the kids still aren’t very good actors. Caspian will be a heart-throb in all the teeny bopper magazines, for sure, but what I saw of his performance didn’t exactly blow my socks off. Of the kids, my favorite was Edmund (played by Skandar Keynes). I thought he was the best part of the first film as well. He has a natural quiet manner that most of the others don’t have.

http://www.aintitcool.com/node/36254

The guy's got taste.