It's an interesting thing: the more these characters learn about each other, the less they know. The less we know, too; once the premise has been established, we're reasonably confident we know who these people are, but as we learn more -- none of which particularly contradicts what we thought we knew -- they become to us as they started out to each other: intimate strangers.

It's a fascinating quality for a character study like this to have. I hate to be down on a movie that is so perceptive about human nature and skilled at portraying it. The problem is, the more unknown the characters become, the less interesting they are. Perhaps they merely overstayed their welcome, and the film would have been better if it had concluded sooner. But I think the problem is more fundamental than that. You've heard of stories with no forward momentum? This one has plenty of momentum; it's just in the wrong direction.