It is warm, and tactile, and feels sort of like people filmed themselves playing with toys, and that fact alone gives the film a kind of sweetness and appeal that most contemporary animation is simply too slick to tap into, and even a stop-motion masterpiece such as 2009's Coraline misses out on, simply because it is too polished.
As in "Coraline," the use of 3D enhances the sculptural technique and lends itself well to dramatic lighting effects, but it never distracts, and the pic won't suffer a bit in 2D.