The 3D is not as perfectly executed as the best contemporary 3D films, but the 3D version adds enough to the experience that it's worthwhile trying to see it in a 3D theater if you can. So says my eldest daughter, who saw it both in 2D and 3D. I only saw it in 3D, but I believe her.
I enjoyed it thoroughly. The film takes Lewis Carroll's books as backstory, and is set about ten years later.
If you watch it, keep an eye on Anne Hathaway's White Queen. Always remember that she is her sister's sister.