Ok some details.
THe preview was written by Tom Francis, he loves Deus Ex.
"Hmm, this kind of is Deus Ex"
"I doubt it will be better than Deus Ex 1, but I think it might be comparable".
Adam Jensen is your name and you were a security guard until some aug'd guys removed your arms.
The story is self contained within the game and is seperate from the other 2 games.
The game is primarily a stealth game, but light levels don't affect it. Adam is able to cover against walls etc and when he does so the game goes into third person, and you can see around corners.
Silent take downs are also in third person, you can take people down non-lethally or use your augs to kill people in a very gorey silent way.
Crossbow is in!
Guards you knock out can be brought back to their senses by other guards, who then hunt for you.
You start with just your arms augmented but you can buy more augs for yourself from a Limb Clinic. These augs can then be upgraded with experience points (a metaphor for Adam Jensen getting used to them).
Augs use energy, no energy and you can't use them. You can upgrade your energy bar throughout the game with new pips and the lowest pip recharges itself slowly.
Augs listed:
Enhanced vision
Mind Reading
Mind Control (like in the trailer where he makes the guy shoot himself)
Cloak
Claymore system
Icarus landing system (jump high, stun enemies when u land)
Strength (more carrying space and upgrade to carry heavy stuff)
Wrist Blades
Hacking module
Mysterious splayed hand abilities.
Running and shooting at people will get you killed, you can die from 2-4 bullets hitting you.
Health regens there are no med packs.
You can't lose limbs (aww).
The city in the trailer is an island city built off the coast of Shanghai by one of the leading cybernetics companies. When the government wouldn't let them expand the city they just build another one on top of it. So it's a double decker island city. The developer say it's bigger than Liberty Island in the first game.
You have a female pilot.
A few characters from the original game make cameo apperances and some of the original voice actors return. The only one that seems for sure is Tracer Tong, who at this point is a computer hacker.
There is an expansive conversation system. Minor characters you just get the information from and move on, but major characters it's possible to have long conversations with resulting in either getting what you want, failing and having to try again or pissing them off so much that they won't ever talk to you again
The example they give is a heated argument Adam has with a mob boss.
Theres a line from Steve Szczepkowski the audio director when talking about the voice actor for Adam "That's his natural tone. I didn't want a mimic of JC, but he needed to sound like he's from the same family." Make of that what you will.
Hacking takes place in real time on screens in the game and is a minigame, screw up and a timer countsdown before you fail. Since it's real time a guard could attack you whilst you're doing it.
Theres a cover system.
You can pick up all sorts of stuff, use it as cover etc or throw at people to kill them.