Why build with straw bale? It's a sustainable resource, and often goes to waste and is burned. Straw bales create thick walls, which are energy efficient. Straw bale homes use untrained labor, like me. They also have a thick rough look to them, which I rather like.
The walls are covered with mud or mud/lime or mud/cement. Most of what I learned at the Earthen Plaster Demo was about how flexible you could be with your mixture both in terms of the components and the application.