Don't delude yourself into thinking you're going to watch a film when you enter the cinema to see this. You're not. You're going to experience yourself, trapped in a hole, and what you get out of the time depends on what you take in there with you.
People who are saying this film is boring unfortunately missed the experience and the whole point of the film; you're not watching a guy in a hole - you're living it. By the end I was a wreck and had traversed the full gamut of emotions.
It's not one I'll be queueing up to ride again, but it's one hell of a trip.