Iñarritu is a genius, and this movie fully realizes his genius. Like Amores Perros, it is an umcompromising portrait of pathos arising from a life that has no solutions. Very grim and almost cheerless, but so vivid, personal and spiritually accurate that you are drawn in completely, and wrung out like a towel. Not to be missed if you appreciate cinema as art, not just as feel good entertainment.
People who hate science fiction adventure movies won't change their minds with this one, but if you enjoy a riproaring space opera, this one is about as good as any has ever been. A few conundra remain, which may or may not have consequences in any sequels, but these can be attended to or not, as the viewer prefers, without affecting enjoyment of the movie as a spectacle.