Well, there are some things already that are almost needlessly difficult to find, like flint for example. Though I'm guessing you meant more in terms of uniques?
Oh, I've managed to get my brother to buy the game
He'll be joining my server shortly. He's been reading about redstone, and being that he's a computer engineer, he has interest in trying to build a working CPU with it.
So yay, I've finished my tunnel:
The interesting thing is, the lighting gives off a blue glow to the water, which I don't think it did before the new lighting: