My tweet sums up my thoughts about the film:
I won't post spoilers, but after seeing the movie and then reading some "explanations" of the movie (not that anything really needs to be explained, the plot is pretty straightforward--but I more wanted to see if there were any details or layers I missed), the filmmakers themselves state this plot is not meant to be a surprise... you were supposed to get where this was going very early on. It was more about watching an inevitable journey and not being able to stop it rather than an original concept. They also view it more as a fairy tale with horrific elements. I encourage your to read some "ending explained" articles just to realize some of the nuances and interpretations of the film. (Do it after seeing the film, of course.)
Another article mentioned they were editing up to the very last minute... which may explain something I saw in the trailer that wasn't in the film... unless I missed it... but did the scene with the bare feet levitating off the ground end up in the final film?