Well, as many Doom/id fans know, Doom 4 was only shown to QuakeCon attendees. They checked for cameras at the door for each person individually, but we have yet to see if maybe someone snuck by with those sunglasses-cameras or mini cameras or something. Luckily, there are many websites/forums that have people who replied to/made articles/threads that go in great detail about the game.
Looks like the main points about the game is:
It uses a new version of id Tech, called id Tech 6 (some call it id Tech 666)
It is going back to it's run and gun roots
Has absolutely brutal fatality moves like Brutal Doom, and the game is very gory
Plasma gun, Double barrel, rocket launcher, pistol, shotgun and chainsaw were shown
Two levels were shown
Game is a reboot, not a sequel
Monsters look more "disgusting" and "threatening", but somewhat resembling of Doom 3 a little
Megatextures are GONE!
1080p 60 FPS on next-gen
A Parkour element is in the game
Movement similar to Quake 3 Arena
Graphics "aren't groundbreaking, but are a lot better than RAGE or W:TNO"
Check out the links below for more info vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
In-depth articles/threads I found:Kotaku:http://kotaku.com/people-are-actually-seeing-doom-4-right-now-1606903942/all
Doomworld Forums: Doom reveal first impressions:http://www.doomworld.com/vb/doom-4-general/69416-doom-reveal-first-impressions/
Doomworld Forums: Doom 4 at QuakeCon:http://www.doomworld.com/vb/doom-4-general/69414-doom-4-at-quakecon/