Speaking from the opinion of someone who doesn't get particularly attached to movies based off of American comics, I think this is a very good movie. I haven't seen all of the movies which Catwoman is portrayed in, but Halle Barry (sp?) fit the character well in my mind. I'm not saying it's a remarkable film, but I found it enjoyable - I don't see why people keep making a big deal over Catwoman's outfit: it's not THAT risque, and it's the essence of the character to act the way she does.
As to the rating, I think I watched it when I was 12 and had no problems; the violence is mostly surface, little blood, the most disgruntling part is likely when one woman falls from a window and it is shown how she landed; mild cursing, mostly stuff pre-teens already know, no f-bomb or anything like that. There's one scene where it's implied that two of the characters have sex, but it's dark and there's no nudity, mostly just kissing then it fades out; other than that there's innuendo throughout the movie.