This film is certainly worth a watch.

The omnipresent threat of the entities that incarnate your worst fear works its way into every aspect of the film, leaving you with an underlying tone of suspense and unease which creates a good overall viewing experience.

To its credit, the film starts of very strongly with a harrowing opening sequence. Further scenes, however, fail to live up to this standard and come off as underwhelming. This is partially due to the lack of development during the film for supporting characters, scenes that should provoque emotion simply fail to do so as the audience has little investment in the consequence.

I'd therefore disagree with those who say the film could've been 20 minutes long, I don't believe 2 hours was long enough for a plot involving so many different stages and different characters. My personal opinion would suggest that it would need a miniseries to do it justice: whilst the action/horror scenes would be yet more sparce, they would leave a far greater impression if the character(s) involved had been given more than just a couple developing scenes.