To sum up, this is a visually beautiful movie that is sterile enough to watch with the kids, and fits snugly as a prequel to The Wizard of Oz.
Nothing here is going to knock your socks off by any stretch of the imagination. In fact, you should simply view it as just back story on the characters from The Wizard of Oz (there is a single notable exception...).
They do a pretty good job of explaining some of the characters, but there are still a lot of unresolved questions.
It's a good film that everyone will enjoy, but again, you won't be talking about it later.
I'd definitely brand it a "see once just to say you did" movie.