We're fairly careful about what they watch (they're 6,4 and 22 months). They generally watch CBeebies, Pixar films etc.
However, they HAVE seen Pirates of the Caribbean 1. Ds1 was DESPERATE to watch it, and he was given it for Christmas. I watched it with him, and he wasn't scared at all. I asked him if it was scary, and he said 'no, it was funny. They shot off each others hats. And the actors are only pretending - Johnny Depp is pretending to be Jack Sparrow. And the skeletons aren't even actors, they're done on a computer.'
I think it's unpredictable what they find scary. This same ds1 cannot watch Numberjacks because of the Puzzler - he is physically shaking and hysterical if it comes on. And Dr Who would be way too scary for him, as would Harry Potter. But Pirates is much more 'fantasy' fighting imo - it's the way they play pirates in the playground - kind of 'bang you're dead' rather than lots of blood and horridness. And Jack Sparrow is a good role model (at least in the first film) as he is very pacifist, and won't fight if he can negotiate instead.
I DO think the story lines of the 2nd and 3rd films (not that I've seen them) are too adult, but the 1st one is fine imo. Having said that, it's not a film that we let them watch again and again as they do with Toy Story and Cars.
It's had lots of benefits - ds1 has spent a lot of time writing his own Jack Sparrow 'books' - 10 or 12 pages worth. And anything that gets a 6 year old Y2 boy to write for fun at home is good imo! And he has also learned to play the music on the piano (I've written it out for him). It's way beyond his 'level' (I'm teaching him), but he can do this because he REALLY wants to. And it has got him interested in other film music - he watched the Lion King 2 today, and was commenting on the score all the way through, and at the end was scouring the credits to see who wrote the music.
It hasn't lost any innocence imo! I'm far more concerned about some of the programmes on CBBC, which we don't let them watch as a channel - I think it's way too adult for a 6 year old - or the adverts on Nick Junior, or ITV - again they aren't allowed to watch those channels unless there's something very good on (eg the original Charlie and the Chocolate Factory).
If I think about what he reads - lots of Roald Dahl - I honestly don't think PotC is any more 'horrific' than something like The Witches, which could even be more pertinent to a child, as the whole book is about a plot to turn children into mice and then set traps and cats on them!
Sorry this is so long! I did think long and hard before they watched the film!