We saw it today. Its a much better movie than the critics are saying it is.
As for whther it would be OK for an 8 year old, I think it would depend on the 8 year old.
Warning, spoilers follow
Keep scrolling down if you want to see what might be an issue for children in this movie....
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OK, You've been warned.
There is quite a bit of violence and one semi-explicit bedroom scene. This take place between a husband and wife and nothing graphic is shown, but it is clear that sex is taking place. The scene leads to a very distrubing rape nightmare. Its short, but its not pleasant. There is a lot of violence, but no more than your average Star Trek flick. And... (here comes the big spoiler, last chance to bail out)....
.....One of the main characters from the series is killed. If your kid is a big fan of Trek, he may find this disturbing.