I love it!! Well Kim Soo Hyun was a big yes for me, having loved all of his shows so far. I was very happy to learn that Yoo In Na was acting here. Even though she will be slightly evil, but I think her role is a very dimensional and grey one which you can hardly just label her as a 'good' or 'bad' character. So far I'm on Episode 4 and enjoying every bit of it. The flashbacks are done tastefully and reveal enough without being draggy (cos flashbacks are always draggy).
I shall finish the rest of the episodes in a jiffy haha.