Watch Dogs takes place in an alternate reality version of Chicago features protagonist Aiden Pearce, a hacker who can control virtually anything through the city's CtOS, a supercomputer that controls and monitors almost every piece of technology in the city. (Think CBS' "Person of Interest" meets the NSA.)
The story trailer provided a look at Pearce's background and also featured a pronounced graphical downgrade as compared to early game videos & trailers. While it seems it may be featuring PS3/360 footage, others have wondered if Ubisoft has 'stripped down' the game to ensure the large in-game world is sustainable.
Also, Creative Director Jonathan Morin confirmed via Twitter that the game will contain an eight-player freeroam online mode.