We enjoyed it - just don't go in with high expectations. DS11 and I were the only ones in my family who had seen the movie - after seeing the exhibit at MGM, DH, DS16 and DS12 desperately wanted to see the movie!
There is a winter scene (with snow) outside the exhibit which is a great place to take pictures. When you enter the exhibit, you walk through the wardrobe doors into "winter". There is a live person as the White Witch who looks a lot like the one in the movie. Then they show some film highlight clips. As you leave, there are some costumes and props from the movie.
If you liked the movie, why not give it a try - it doesn't take that much time. I agree they probably could have done more with it though. You'll probably get lots of different opinions here.