Finally! We now have a new Minecraft snapshot. This one contains MAJOR changes, including world generation. Firstly, there is a new world type. There are now:NormalSuperflatLarge BiomesAmplifiedCustomThe last one, custom, lets you customize how large the mountains get, how high the sea will be, disable/enable certain structures, and much much more.
Another feature is that now you can have WORLD BORDERS. This means that now, there will be a way to limit how far players go in SMP without having to use ugly bedrock walls. You can enable it with the /worldborder command. It bascially makes a visible wall, that you can actually see through a bit.
Here are is a gif and screenshot (by the developers):