New Minecraft Snapshot-12w21b

As many of you minecraft lovers probably know, minecraft is releasing weekly pre-releases. The latest is called 12w21b. Get it here!
Here are a few of the awesome new features that were added:
Writable Books
Trading with Villagers
Pyramids
Desert Villages and Desert Wells
Emeralds and Emerald ore
Ender Chests
Coaco bean plants
And much, much more!
Screenshots:

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How to install (Mac)
Go to the folder Library (may be hidden)
Click on a folder inside, called Application Support
Click on the folder called Minecraft
Click on the folder Bin
Rename minecraft.jar as minecraft2.jar
drag in the other minecraft.jar that was downloaded into the same folder
Done!

Windows how to install coming soon!

How to uninstall (mac)
Go into the same bin folder as before when you were installing
Rename minecraft.jar to minecraft3.jar
rename minecraft2.jar to minecraft.jar
Done!