I share your enthusiasm. I am at work, and still can't stop thinking about it. Which might surprise some, as they might have been bored. To be sure, it moves at a glacial pace. But that is as it should be, I think. We are watching the full arc of a character's development. I can't decide whether this vision of a Life is nihilistic or hopeful. The name Sandy, itself, is evocative of the arid, implying a Life that is, in some ways, desiccated, drained, eroded, and dead. I'm not sure if she was better off before or after "the incident."
At the end, I expected some expository dialogue between Sandy and her mother (or with Baird) to go into her feelings more -- to make things explicit for the viewer and define exactly all the things that might be going through her mind. Neatly sweeping things up, so to speak. But I am glad the director and writer chose not to do so. It gives the movie an oceanic feeling, a "real" depth. Sandy's reactions are complex, wide ranging, and clearly seen on Collette's face. But we never get to hear all the things that are on her mind. Which is as it should be, because that's often the way it is... and thus giving it that depth I sensed. I can almost fool myself into thinking that these are real lives.
I saw the film in its brief U.S. theatrical run, and I share the appreciation of it. Among its many virtues, its almost a textbook example of how to use the "epic" widescreen frame for an intimate, personal story. The film makes spectacular use of locations (the mining scenes really stuck in my memory), but the breathtaking vistas are used primarily to show you the isolation of these two people on their unexpected adventure together.
Collette tends to be known as an "emoter" because of roles like The Sixth Sense. This film confirms her range as an actor, because this character would rather do anything than let her feelings show.