Thought this was a very good film, but that it should not have been a PG rating. It was very scary in places and extremely loud with some revolting aliens. DS3 (7) was pretty distressed fairly early on and it didn't improve much as the film went on. Obviously all children are different, but I wouldn't recommend it for under 10s.
Other adults as we were coming out were commenting on how full-on it was and that some of the children in there should not have been there.
Thing is I've always thought that PG related to a parent's view of how their children will cope with a film, not that parents should view every PG film in advance. DS3 has seen plenty of other PG films without any problem but he was very unhappy in this one.