X-Play's Abbie Heppe explains there are a few major differences. One, dead players will stay dead unless revived with a defibrillator -- keep in mind that each player can carry a defibrillator or a med kit, not both. Second, zombies must be killed with headshots, though it's hard to tell how strict this rule is in the video. Third, players have to be much closer to items in order to pick them up. Finally, there are many, many more witches. See it for yourself after the break.
[Via Evil Avatar]