WTF? I am not often a swearer, but in this case...
That ending I wouldn't have minded in some dramas. But I really felt like this one didn't know where it was going or what kind of drama it wanted to be. The ending felt rushed, and at the same time I couldn't wait for it to be over. By the end there wasn't a single character I liked, which maybe was the point. But it felt like they lacked the courage to really commit to the darker side of the story, so it ended up feeling like the ending just flew out of left field. (For a minute I thought he was going to jump, and what a terrible ending that would be... I had no idea how bad it could get...)
Overall, by the time I realized I wasn't going to like where it was headed (around ep 16 or so) I was past the point of no return (for which I suppose I should give them credit). I don't know, I feel like if something had been done better they could have had the same surprise ending and I would have been both totally surprised, and at the same time felt like it was the right ending. For me, it was not that drama.