I took my young son to see this movie, and I don't understand its PG-13 rating. Aside from a little language (you can count the "bad words" on two hands) and violence (95% of which is robot-on-robot), it is a perfect movie for little boys.
We cheered Atom (the main robot "character"), along with the rest of the audience. I also liked the fact that it wasn't a storybook ending. My hunch: Expect a Real Steel 2.