Although I do think I read a few too many spoilings materials early on. Oh well, doesn't matter for the second viewing. Also I'm almost certainly going to buy the soundtrack. I might do it at lunch in an hour or so.
Now as for the question lampbane raised. I found Pan's Labyrinth more entrancing and timeless. However, there's something to be said for timeliness and Children of Men pulls it off very well. I'm still fond of my personal not particularly ambigious reading of Pan's Labyrinth but Children of Men is certainly the movie with more mature and sophisticated themes. For those fond of political readings, CoM is by far the more interesting film. I would strongly recommend it to anyone that enjoys this sort of thing. I would also recommend seeing it in theaters, the craftsmanship is excellent and it benefits from the big screen.
In the end, I was more gripped by Pan's Labyrinth and I think that film appeals to a wider audience. However, I think that's the nature of the genre. Fairy tales have a certain primal widespread appeal. Distopian stuff is inherently hard and even the best stories can be rather painful. I think this limits the appeal even to those, like me, who like this sort of thing. As a side note, I think that gets to why I particularly liked Now and then Here and There. The protaganist in that film was a straightforward hero, not an antihero. That's obviously easier to pull off when you've got an insertion plotline but so be it. The story was just as grim, and at times grimmer, than Children of Men but it was also in some ways easier to take. This isn't a weakness in Children of Men, Theo is a good character, but there's just a certain distance innate in distopian.
And thus ends this spoiler-free post. I'll later make a full spoiling post to allow for more discussion in comments.