I like the thing that he has planned many things very carefully, even if it havn't been so much of importance at that moment it's introduced. Like the cursed seal: As the story developes we have learned that it has a powerful "Stage 2" and most recent we now know it's origin. Not at all what I had suspected from the start when Sasuke was bitten. I thought of it more like some kind of poisonous mark.
Or Sharingan. We learned first it copied techniques and we also learned it made the user the advantage to read the opponent's movement. Later we learn it could hypnotize the opponent and be used in powerful illusion-techniques. And then even further in the story, we learned it had a different shape that made it even more powerful.