Yeah, I'm in the process of clearing out this massive monstrosity of a mine beneath my 1.8 base that I'm currently working to build a sky-rail back to my 1.7 land.
It actually looks pretty badass, as it looks like there was a massive earthquake which destroyed the mine. The main cavern is an underground ravine that has abandoned mine-pieces floating around in it. I intend to pick this place clean. I've already murdered four spider spawners.
I'd love to locate a stronghold or a village at some point, but the abandoned mine just gives this incredible self-sufficiency that hasn't been possible in Minecraft up until now. You could stay underground for days in-game and still have enough supplies to keep going. Between eating rotten meat from zombies (which is actually healthy, to my surprise), random bread in chests (how gross is that?), to all the wooden planks that you can turn in to torches and tools.