From Minecraft Forums:
Spawns in dark caves
- Added a passive mob (Bat)
Sleeps during the day
Hangs on the ceiling when idle, starts flying when players come near
Throws splash potions of poison, slowness, weakness and instant damage at you
- Added a hostile mob (Witch)
Regenerate health over time
Hold an empty bottle and rise their noses when attacking
Drink potions of instant health and fire resistance to defend themselves in combat
Rarely drop potions of instant health and fire resistance
Is immune to some splash potions
Does not spawn naturally (yet), but a Spawn Egg exists for it in Creative Mode
And the bats still look cute.
Dinnerbone says that the witch is only 1/3 finished.
Tobias Hibbs @Sirhibbsy - Hey! Hey! Can you promise me this: Witches will have broomsticks, witches will have pet cats, witches will spawn in huts
I can give you 2/3
Witches: Yes, they're just a villager with a hat. That's intentional. They're also only about 1/3rd finished. Keep this in mind!