Great story and expansion to Subsurface, waiting for a sequel. I was lucky enough to get the most satisfying ending on my first playthrough (the one with Marc), which is the most unexpected one, awesome. But the other endings just follows what you'd expect, and considering how the third act is rushed, they feel quite mediocre.
I was very pleased with my first playthrough and will rate accordingly, but the game sure goes from 8 to 80 depending on your choice.