Ok the wiki is saying stuff about this
What changed in the update
it was released like 20-30 minutes ago
http://www.teamfortress.com/blizzbobarrabas/it appears that there is new mvm missions with zombies (but with robot sounds)
a new special map with a "Wheel of fate" that gets spun every time the cap point gets capped with special occurances or something
Spells to cast on your items that give them special effects, like shifting colors "ghost summoning, flaming footsteps and more!"
haunted voodoo souls that make you look like a zombie on full moon/halloween days