I think they mentioned it was on default, standard difficulty. They say they have higher difficulties (implying more then one, so at least two) where acid does a lot more damage (or any since the acid on what they showed was like spicy water, a little irritation), you have few or no respawns, modifiers for example to make only headshots and weak points do any damage (I'll be using that one) and I can assume raise the damage the aliens do.
It does bum me out that they're showing only the lower difficulties, though we haven't seen much footage at all and the journalists aren't the best players, especially when they have to do live commentary, so I do understand. I'm all for having different difficulties (though that does divide the community in online games, like it did for Bug Hunt in ACM), I just hope they give the hard core crowd a good ramp up in difficulty, and more of the simulation feel (the exact words they used recently, so I'm hopeful).