The mystical part of the film surprised me. From the trailer, it looked like more of an action SF kind of story. (Especially with the shots of the 'space marines') As for the plot, when I'm asked to describe it I tell folks that it's 'very Japanese'. It reminds me of an anime. (Of course, 'The Matrix' reminded me of an anime as well.)
But I enjoyed it immensely and really got into the storyline while still marvelling at the absolutely gorgeous overall look of the film. I found myself actually caring about the characters. (So much so that I got misty when the female space marine died.)
The voices were well-cast. It was a kick to hear Steve Buscemi as well as Peri Gilpin (Roz from Frasier). I think Peri has a very sexy voice which can also be quite commanding. The basso tones of Ving Rhames were welcome as well.
I'm not sure why some folks (mostly movie critics) seem to be down on this movie. I suspect that they had trouble following the story and that seems to irritate film critics no end.