My husband was very enthusiastic to take our six children (twin 6-year-olds, two 8-year-olds, a 12 and 14-year old) to this movie. I figured it is a Disney movie, rated PG so most likely ok. I even read the other reviews on this site before taking them. The previews alone were enough to frighten the 6 and 8 year olds due to the content and "dark" feelings. They were hiding their faces through most of them (we're talking about kids that have seen Transformers 1 and Harry Potter.) Once Tron started, it was apparent 10 minutes in that the story was beyond the scope of the five youngest children. Even our 12-year-old had several questions throughout the movie... "who's that guy, again? Is that his dad? I thought that was his dad?" I would say 12 is the youngest that could grasp the general concept of this movie. It is also VERY slow moving in parts, leaving the younger children awfully restless.
Much of the movie had battle scenes that were gladiator-style. While there was no bloodshed (with the exception of one drop), I still felt it was pretty violent and dark. I think the little kids came away with the perspective that the "white/blue guys were killing the red/yellow guys," and one guy was trying to find his dad.
My husband, a big fan of the original Tron movie, was very disappointed in this movie. He said very little related to the first movie, and it was very boring. The graphics were good, but the story was weak.
Not a movie I would buy or recommend taking small children to. Glad we didn't waste our money on the 3D tickets!