Michael Jackson is gone due to a legal challenge, and replaced by Disco Stu.
More interestingly, there's a new Create-Your-Own-Zombie mode, and a few new achievements.
And more importantly, I would advise: don't run it. Seems horrendously buggy, and some of my save data was missing. Could be my machine specifically, but it's always run perfectly before so I think it's a problem with the update... we will see.