Once Upon a Time in the Underground (Minecraft cave prototype)

On Minecraft Live Oct 3 we announced the Caves and Cliffs update, which includes (among many other things) new cave generation. Here is the extended version of the cavegen demo we showed there. What kind of caves would you like to see in the Caves and Cliffs update? Inspire us! Post links, pics, videos, drawings. Some disclaimers about this demo: - The mountains at the beginning and end are only placeholders (the actual mountains will look quite different). - We use glowing ores as a placeholder for new