There seems to be consensus that this movie's too long. That wasn't my takeaway, given most of the performances, characters and situations were compelling enough to sustain interest over most of its three hour run, enough to make it feel fluid and not sluggish. Where it fell apart was in the unearned, "character arc" ending, making all that came before seem pointless. This movie for most of its three hour span is about how the audience views/judges the protagonist's choices and judgment, and then in the last few minutes, it shifts to being all about a young girl's emotional journey from Milan to Minsk.
The meta-criticism of this movie is that it seems like Lonergan tried to repair his half-baked ending *after* filming had ended and it was theatrically released by including material that just drew out the build up to the unearned final "emotional breakthrough" scene, when what the logical structure of this movie really called for was something more ambiguous, open-ended and inconclusive, something to make the viewer wonder rather than a therapist conclude. If I were ever going to argue against the concept of character arc, I would use this movie as a prime example of how limiting and useless such a notion is.