So GTA IV's DLC will be out in the "Fall"? Awfully vague, Microsoft. There's three months in the Fall. We like things a little firmer. Like this claim by RPG-TV - based off an Xbox press event held in London - that GTA IV's DLC will be out in November. And when it is out in November, it'll add "roughly 15 hours of additional play time". If true, 15 hours is a looooong time. Too long for it to just be new missions on the same islands.
Preview of New XBox Experience [RPG-TV]