This drama is captivating from beginning to end. It's important not to miss details...small things mean a lot. It'd be fun to watch it again to see what I missed the first time.

Things I liked:

1) Female lead. I liked her much better in this drama than in "To Fly With You" (can't seem to get past ep 29 in that skating drama...) I like when she breaks the 4th wall. She does a great job in this drama, playing herself in different ages convincingly.
2) Male lead. At first, I thought it was an interesting casting choice. It's still interesting, but interesting in a very good way. The actor is perfect for this role. He's very natural in it. After finishing the drama, you really can't imagine anyone else playing the ML.
3) Story. I like what if stories, but sometimes they can be done wrong. I like how the overall message reiterates that as much as you might want to live in the what if, reality is where you need to be and where you can make a difference.
4) Good handling of "others." I don't like dramas where the "others" are constantly trying to sabotage the mains' relationship. There might be some competition, but it's not petty.
5) Ending. Justice prevails, and there is hope. I like that.