We just returned yesterday. I was REALLY looking forward to the Narnia exhibit and was disappointed. We were probably the 2nd group of the day and had to wait less than 5 minutes to get in. You walk through big "wardrobe" doors (my lame description sounds cooler than it actually is) into a winter scene room. There were only about 12 people in my group so we were allowed to sit on the white "snow" astroturf floor to watch the movie trailer. There was a short interactive scene with a White Witch robot. After the movie scenes (which were good, but not worth a long line if you've already seen the movie...) they ushered us into a tiny hallway with a few movie props in glass cases. Like I said before, there were only about 12 people in my group and we were crowded in that hallway. It totally reminded me of walking through the trophy cases at my old high school. The props I can think of were Lucy's dress, a few "frozen" statues, the witch's sleigh, the witch's wand and possibly 3 other things.
This exhibit is only worth seeing if you have little to no wait and you will probably still be disappointed with how minor it is.