That Dead Space 2 issue of Game Informer has hit people's mailboxes, and it's full of proper details on the game. Like the fact Isaac will now speak. Let us all take a look, yes?
First up, the game is set on a space station called "Sprawl", built upon the husk of one of Saturn's moons. It's big; a lot bigger than the Ishimura, and has whole themed wings, like residential quarters, public spaces, etc.
In terms of gameplay changes, you can now not only walk and jump around in zero-G, but fly/float as well, and you're able to shoot your weapons throughout.
Oh, and there'll be multiplayer. No real details on that, but really, you had to expect it.
That's the general gist of things. You want more the really fine details, you could always grab a copy of the mag.