Unique, beautiful, and surreal. Looking back at the film as a single complete work of art, it's great. It's showing something we've never seen before. It's worth sitting through... once.
The shots where the camera may fly outside of a building for 5 minutes just to float around and float back into the building is unique and necessary to add to the realism of trying to represent what the "trip" of death may be like. But if you're sitting down ready to watch a movie in any convention sense of the word, you're going to be bored out of your mind. I'm sure the director himself wouldn't disagree with that.