NEW DATAMINE BY TEAM LIQUID: (SPOILER ALERT!)
Holy spoiler alert. These guys got everything from new skins, achievment avatars for both multiplayer and campaign, and a plot summary for the campaign. This includes a brief summary of what each mission entails, and how it ends.
I'm not going to read that if it's going to be a total spoiler. This isn't some movie where it's not that big of a deal. I will wait till I have the game loaded, and figure it out for myself.