I'm not going to give this a rating. For personal enjoyment I'd give it maybe a 5, but I feel it's probably better than that.
For me, the problem is I just can't relate to this. After watching the first half, I decided I just wasn't into it, so I read the synopsis, and you know, it's interesting, but I just never found this especially engrossing.
I think the problem is, I just don't care about Christianity. And even though this attempts to really think about religion in a different way, even though it deals with interesting issues, even though it would probably offend a lot of Christians, it's still a movie centered around the Christian god and Satan and that just doesn't interest me. I feel that certain movies rely a lot on deep-seated Christian feeling, and that always fails with me, whether it's The Song of Bernadette, The Last Temptation of Christ or the Exorcist. This is not to say I dislike all movies with a Christian bent - I really enjoyed Come to the Stable and Lilies of the Field - I just don't like movies where you need to care very specifically about Christianity, as opposed to just caring about people.
And that's why I don't feel it's my place to rate this movie, because it's a movie for people who care about this. I'd say it's a movie for people who, at least a little bit, believe in the Christian god (and probably not a movie with strong faith in some other religion, since it basically says the Church of England had it right). I am just not this movie's target audience, and while I found it quite dull, I am willing to believe that others would find it fascinating.