Without giving too much away:
Mater struggles with being "an idiot," which is not a new topic. However, as always, Pixar handles the conflict with amazing ability. As Mater-fans all over the world already know, Mater is no idiot. Mostly it's fun, and I think car geeks and techies will get the greatest kick out of it, but it certainly was entertaining. Although the movie's focus is more on Mater, Lightning is still in the movie spotlight, and he learns yet another lesson on friendship. At no point during the movie did I want to say, "This is another one of those stupid sequels about a supporting character," or, "Oh how cliche!" Although the concepts weren't new and the "revelations" predictable, Pixar doesn't lay heavy on the dull. It worked out great for them! The set up worked, the build up was smooth, the climax took an unexpected turn, and the resolution was perfect. (And who doesn't need a few dents? ;) )
None of the trailers I could find do this movie justice -just watch it.
This gets my nine out of ten, and a D (see sidebar). Be advised the images are sometimes intense and the vicious actions of one or more cars may be too much for young children.