Since this was frequently asked in the rumor thread I thought it was only reasonable to post a summary here:
Flamer
Like 1st Ed and effects a section/tile not a square and lasts till start of SM's next turn. However genestealers that survive are NOT free to move within the flamed section and must now roll again for each flamed square they move into. No mention of a reload.
Overwatch
Like 1st and 2nd Ed except all jammed tokens automatically vanish at the start of the SM's next turn. You stilll have to pay Command Points to unjam during the 'stealers turn. However clearing a jammed bolter also returns you to overwatch.
Also Overwatch now gets a continuous fire bonus and kills 'stealers on a second and subsequent roll on 5 or more. Overwatch has become much more lethal
Guard
New. Overwatch for close combat. Allows SM player to re-roll close combat dice.
Brood Lord
What no Patriarch? I'm still calling mine PatPat requires two simultanous hits to kill for ranged combat and for close combat rolls 3 dice and adds the lowest and highest to get his combat score! *gulp* Thats an average result of 7 and more than most SM's can ever roll.
Assault Cannon
No critical explosion on rolling a triple until after a reload (thx L Squinty)
Timer/Command Points
Due I imagine to the fact that the game comes with an egg timer the duration of the SM players turn is now fixed unlike the 1st ED where you got 2 minutes the 30 seconds for each living sgt or captain. In the new edition having a live Sgt allows you to re-select your command point chip if you don't like what you got.
Librarian
In 1stEd Deathwing Librarians got 10, 20, 30 or 40 psi points per game and could add as many as the want to their +1 close combat roll. In the new game they get 20 points BUT can add them after their close combat roll (thx Patriarch) so no waste!
Chainfist
Now automatically destroys doors for an AP.
Lightning Claws
Now 2D6+1
Stealer Movement
Stealers pay 1AP to move sideways, not two. "Free turn" is now part of the action, rather than a discrete action - this cuts down on potential overwatch shots.
Stealer Blips
Stealer blips once used are now placed into a discarded pile. Once all are used up the discarded pile is shuffled and you start again.
Shooting into Rooms
Unless standing at the entrance to a room or inside the room a SM may only see/shoot into the squares directly infront of him.