I was shocked by the violence when I first watched it, which is odd because it's not one of the most violent films I've ever seen. It's something about the way the violence is presented that I found visceral and jarring, but it worked so well for the atmosphere. The outback becomes a landscape in which human bodies are reduced to the inanimate, base matter that surrounds them in the wastelands. The setting really is a character in the film, an agent on par with the hapless humans who people it. It's one of the only onscreen westerns I've seen that reminds me, in certain ways, of Cormac McCarthy's novel Blood Meridian.
And the political undertones are subtle and tasteful--national and ethnic identities, Australia's history of colonization, etc.