Story: Story wise, the fantasy/supernatural element is so superb and very unique! i think you don't see any shows about a girl falling in love with an alien (not that green gross kind of alien but the Kim Soo Hyun type of alien, very hot!) not is it very romantic there is also an element of comedies, drama and a little bit of historical setting which I liked very much.
Acting/Cast: Hey! how can I complain? this is one of the best of the best of it's time when it was airing, Kim Soo Hyun and Jeon Ji Hyun? Their chemistry and acting was fantastic! I fell in love, hated and cried with them!
Music: I love all of the OST! I had everything on my phone!
Rewatch value: I can't count how many times I've re-watched this masterpiece!