Yeah, zero lava and one water used for cobblestone, one millibucket of lava and one bucket of water for smoothstone, and I think it is one bucket of both lava and water for obsidian. It is a wonderful device. No power required, either!
Yeah. It's one of the most under-appreciated machines in TE (up there with the steam engine). For folks who do not know: just remember that this device can go crazy out of control if not controlled carefully. Buildcraft gate logic on the output is the bare minimum you should be able to do.