I think the concept is certainly one of the more original ones in recent history but I still think that the gameplay is going to get old really quickly if the stories for the missions don't change. At some point, you're just shooting waves of creatures for really no point at all. You don't know why you're doing it because the story is somewhat all over the place and you have no idea what weapons you're looking to get. You're just shooting them in hopes that something gets better or you get to go to something new.
I'm just shooting to level up. Why I am leveling up, I have no idea now taht I think of it.