Between the time Monsters vs. Aliens (2009) was released this past spring and today, 3D has gone from being the hope of the future of film to a possible fizzle, given the lukewarm reaction to the recent release of A Christmas Carol. I didn't see MvA in 3D, so I can't comment on that aspect, but I suspect that a film that relied utterly on 3D for audience success would constitute rather thin gruel. I am still not convinced that the most important thing about story-telling is the representation of spatial environments. Novels and plays have been doing pretty well without them. (Yes, plays are in 3D, but unless you are seated on the stage, you experience them as a 2D event.)
The film is the usual underdog story, albeit very funny with some first-rate voice acting. It also sports some feminism utterly appropriate to children's developing minds, and I am sure I would have enjoyed watching this with my daughter when she was a kid--she was bonkers for this kind of feisty self-realizing heroine.
What I found most interesting was a behind-the-scenes feature which, in a couple of shots, showed one filmmaker holding something like a camera, "pointing" it at the virtual environment and manipulating its viewpoint just like a live-action camera. Animation has long simulated the live-action camera with pans and zoom-ins, and short focal lengths have been a feature for at least the last 20 years. (The camera eye has a small area it can keep in focus compared to the human eye--cartoons have learned to simulate this flaw in order to be more "convincing.") And animation has been simulating the hand-held look a long time; but until now that required advance planning and careful execution. Now it appears that handheld and other freeform modes of cinematography can be created in animation in real-time, "on the fly." This can only increase the naturalness and expressiveness of the form.