Minecraft wiki entry for Development_versions, associated text: Superflat world type.
Updated create world screen - now includes Superflat, Infinite and 'old' world types.
Unlimited worlds.
New falling mechanics for sand and gravel.
New insta ticking of water and lava.
Grass and foliage colors for different biomes.
Water color for swamps.
Added more spawn eggs in creative.
New interact button (to make the game easier for new players).