Long story short, I didn't like it very much. I found it very sad and boring at the same time, which is a weird mix.
I didn't feel any chemistry between the two leads, but probably because I found out I don't like Suzy as an actress (it's been the first show I watched with her and I had high expectations... now I'm disappointed).
The only saving grace it's Kim Woo-Bin whose acting, though a bit over the top in a few instances, is far better than Suzy's. Finally, the unhappy ending is unfulfilling too but, to be fair, they tell you what is going to happen since episode #1.