One thing worth noting, in my opinion, is that this has an API. The official Minecraft build is supposed to be getting an API as well, and I'd suspect that it will be similar to this API (but I could be wrong).
Has anyone succeeded in getting this running via ssh and X forwarding and XQuartz? I just get a black window when I start it. I guess I should just hook the Pi up to a TV and try it that way.
It is free to download and play, but this version runs only on ARM processors. So if you have a Raspberry Pi or some other machine that runs a version of Linux on a device with an ARM processor, you're good to go. These machines are generally slow and have limited RAM and disk space, and Minecraft Pi doesn't have the functionality of the full version, but it's free.
I have a Raspberry Pi and I may look into Minecraft Pi to see how it looks as way to get young kids started with "programming". For kids who are already into Minecraft it looks like the Python API is a good way to get their feet wet.
Also, here's a guide someone wrote up on using the prerelease pi.minecraft API, which might help you get started: http://www.stuffaboutcode.com/2013/01/raspberry-pi-minecraft...