1.9 includes:

New mobs
Villager
Magma Cube
Snow Golem
Mooshroom
Blaze
New blocks
Nether Bricks
Nether Stairs
Nether Fence
Lily Pad
New items
Blaze Rod
Ghast Tear
Nether Wart
Gold Nugget
New generated structures
Nether Ruins
Can no longer jump repeatedly by holding a key
Snow golems do not take fall damage