Yesterday a PR rep for Sega reported that Platinum Games "hadn't really gotten the motion controls down yet". The fact that MadWorld was not playable was so that journalists didn't get bored with the controls, and start labelling them "unintuative". Sega wants to finalise the controls before letting the public play it, say Kotaku.
A concern of Sega is that people will tire of MadWorld before they have even played it, due to its violence and quirky graphics. With so little facts on the game, members of the press are quickly writing the game off as a violent blood-fest with no story.
Sega has confirmed that the game does have a story, but it does not want to give too much away. I wonder if the idea for sawing heads off and throwing corpses into giant fans came before or after the plot was written?