You're right. It's going open level, better online, more action (jet pack, melee), more destruction, plus 3D together.
The open level does not promise more interesting gameplay/interaction. Online is under-wrapped.
From the marketing material, I get the feeling that they are working very hard on the (720-targeted) 3D visuals and set pieces (which I like), but am worried that they get carried away. The press demo dwelt on 3D, jet pack, explosions/destructions and melee, which is expected. The actual combat/gunfight mechanics became secondary. I hope they don't forget about basic stuff like enemy AI (teamwork ?), pacing, level design, gunplay, etc.
EDIT: Oh yes, they did talk about revamped aiming. Will have to see how they manage everything together.
In comparison, DS is about very basic exploration, encounter and reward system. There is not much fanciful visual effects. The nice looking things (e.g., the bosses, environmental hazards like the dragons) are all interactive and "touchable" by the character, just like everything else in the game. Little details are overflowing with "personality": from the way the NPCs behave, to every single combat move, every step taken (Look, messages on the floor and white ghosts everywhere !), and death.
