Marines get a new class to help them kick nasty robots and aliens off their ship - the Engineer. Submachine gun? Check. Hacking consoles and PDAs? Check. High tech looting? Check check check.
The new perk system is available upon Squad Creation. Extra Laser Sight damage. Bonus enemy spotting experience. More Hulk Suit flamethrower carnage. You'll need it for the new Medical Deck boss... the Brainien.
Full changelogs are on the discussion forums!