My non-spoiler review? Not a kid's movie, but more of a teen-on-up flick. Quite true to the comic book standards, and yet there is a solid story line to it. That's one thing I like about the Spidey flicks versus Fantastic Four or similar movies... there is a good story that just happens to be about a superhero (versus a special effects movie that may happen to have a watchable plot through it).
Here's the biggie, though... lots of hero confusion. By this I mean you see "good guys" doing "bad guy" things, and vice versa. This is one reason why it's not so much a kid's flick (in addition to the intensity of the movie) in as much as it is good discussion fodder for each of us to look at the actions and motives of a person's heart (as both specific and collaborative). Maybe that's why there is appeal to these movies... we all know what it means to wrestle with both the light and the dark on the same day.
"I do not understand what I do. For what I want to do I do not do, but what I hate I do. " (Romans 7:15)
If you don't mind spoilers, here is a site with some clips: http://www.sermonspice.com/page/spiderman3
P.S. Be careful if you comment on this post not to give anything away.