i'm guessing the lower rating comes from the surprisingly small amount of visible blood. they tend to judge violence by blood a lot. and, while the reavers are really very scary, and the whole miranda thing is...ugh...can we say nightmare fodder?...there's very little blood.

still, you're right. it was far more violence than i'd expect in a pg-13 movie. i had no idea what the rating was until you mentioned it. i just knew i had to see it. :) i am immensely thankful to mr. whedon, though, for having a sense of humor that helped ease the distressing/scary/sad bits. it cleared your mind for the next incidence.