The enemies come from BELOW instead? OMG! There's a plot idea we've never seen before!!! =_=...*Rolls eyes*.
Ok that asside this could be really good if they hit us with as many set-pieces as this trailer makes it look like they will. Of course the gunplay is important but the set-pieces are what define the world of an FPS which is what makes you care about it and the characters within it. I never did get to play the first as I never had a PC that could handle it, but I'll keep my eyes peeled now and see if it looks worth checking out once it's closer to release.
Oh...and to the person above crying about how it doesn't look as pretty as it could, please go eat a bullet. Graphic whores are murdering gaming. This game looks wonderful in terms of graphics, after a certain point there's just no reason for the graphics to be any better. Could they? Sure, but they'd be sacrificing time that could be spent ironing out gaming and story issues, things that actually matter in terms of a GAME, while graphics are a purely aesthetic issue (especially at the point these are, the transition from say PS1 to PS2 graphics brought with it game changes since you could more easily differentiate items in the world, but now such improvements are done and over, any further graphical improvements are merely to rope in the people obssessed with having the preeties game).
If you want graphics go watch some movies or something.