The reluctant hero is a pretty tired premise, but this movie doesn't emo it up too much. Some of the dialogue is kind of lame. That's the bad stuff.
As for the good, the production design is gorgeous. The 3D is actually a benefit instead of a surcharge. Elfman's score is great. Rachel Weisz is the best of the witches, but the weakest link, Kunis, is still good. Kunis nailed the cackle. The plot is very cunning in the way it dovetails the musical. The foreshadowing is also very smoothly done. Ozma and the silver/ruby slippers were neatly excised. Franco's performance as reluctant hero more or less successfully hid the staleness of the idea. He usually seemed to at least be alive, if not charismatic.
And yes, the china girl was amazing.
Overall, I'd rate it B+. Nearly as good as Return to Oz.