I haven’t seen it myself, but my 6-year-old went with a friend for a birthday party and enjoyed it.
Full disclosure – we’re very liberal about what we let our boys watch at a fairly young age, no sexy stuff/very bad language, but they are used to scary/loud action and moderate violence. (Think Avengers, etc).
Hubby took me to see it when the boys were at school one day, just to screen it first. We thought it was GREAT and there wasn’t anything too bad in it, we’ll be letting two 6-year-olds watch it when the DVD comes out!
We’re pretty strict with what we let the boys watch, there are just some things I don’t want to have to explain yet! They too watch a lot of super hero violence though!