Terry Gilliam shows his ability to write an engaging story with unpredictable twists and turns. The actors can act, the special effects work to provide sufficient but not overdone eye-candy, and the story feels like it came from a classic novel or a well-known fairy tale (The Brothers Grimm on a particularly grim tear).
The story is the main draw. It's bright as the morning star and packed with Gilliam's own imagination. There's no place in the imaginations of the main characters that it won’t go, and it's always two steps ahead of the viewer. The plotting is tight and energetic, going helter-skelter when it makes sense and converging to a needle-point when demanded. See it on the big screen. Not appropriate for under 12.
I was expecting a mostly teen-oriented movie, but it really does speak well to over-30 adults. The audience was mostly composed of teenage girls, Twittering and giggling whenever Zac Efron exposed an ab; but that made for a happy, enthusiastic audience.