I made it a point to see this in IMAX 3D and was VERY VERY happy I did so.
The 3D effect, as Scott said, was very pleasant and added to what in many ways is a "novelty" film to start with.
The whole film felt like a 3D paper doll presentation and I enjoyed it very much, as did my youngest daughter (8) who loved OZ the great and powerful.
They did a really great job cleaning up the movie and the 3D was tastefully done.
While it is a shame it didn't run longer than one...