Minecraft wiki entry for Development_versions, associated text: Powder snow’s hardness was slightly increased, from 0.1 to 0.25.
Freeze time has decreased to 7 seconds and hurt frequency has decreased to 2 seconds.
Entities on fire now melt powder snow when colliding.
Increased vertical movement speed within powder snow (entities fall through powder snow faster).
Mobs now shake when they are fully frozen.
Entities wearing leather boots falling from a height of > 2.5 blocks sink into powder snow instead of landing on top of it.
Applied fog effect while standing very close outside a Powder Snow block.