Seems like it could be cool. But I still like zombies better.
It's sort of interesting, played this mode for just a few minutes today. It's a completely separate mode (it's own .exe) and has it's own progression and perks. It's essentially horde mode against aliens with progression. The couple of maps I did play of it were like this...you pick up a drill, move it to an alien hive, plant the drill, then wait for a timer to countdown while you protect the drill from aliens who are intent on destroying it. You earn skill points to level up your character, and earn money by killing aliens that you can use to do things like drop ammo for your teammates. It's almost like horde mode with some vaguely moba-like elements thrown in. It's a cool side bonus.