I remember when everyone was crazy about the SkyBlock Survival Challenge... but it was just too easy.
With all the new NPC village features in the snapshots, it is possible to survive on super flat mode. For example, with iron golems you can get infinite iron, which means buckets, which means cobble farm, etc.
Just an idea, maybe someone can try it out and post a couple of vids.
It was already possible to survive without the golems. You could get iron ingots and saplings from blacksmith chests, so you could get a cobblestone generator and infinite wood. On top of that, I imagine it would be quite hard to kill iron golems in a new world. I'm glad people are taking interest in this idea, though.
Also, you could get wool from the lampposts to make a bed, so your spawn point doesn't change when you die.
If you're having trouble finding a village with good resources, I posted a seed a while ago: http://www.minecraftforum.net/topic/968942-a-good-superflat-survival-seed-with-no-exploration-required/