Do you know how hard it is to act 7 different characters convincingly? No? I don't either. But JI SUNG EFFING DID IT OK. And you could tell which character he's doing just by his eyes and facial expression. Even if you're not into plot lines like this, watch it for the acting. This drama pulled me into the Ji Sung fandom.
People also will tell you that this would be the one drama where the male lead is the same actor as the second male lead for whom you would get second male lead syndrome. Let's just say the main character's alter ego is also very charming and attractive in his own way and there's a whole fandom for that.

The plot line was super interesting, the acting was superb.
And spoiler alert, Ji Sung and Park Seo Joon won best couple in the drama awards that year. With each other.