I loved IU in this, she was great, Yeo Jin-goo on the other hand not so much. As for the other characters it's a mixed bag really, there were some great ones & some really weak casting choices. I loved the audiovisual experience, whenever beautiful cinematography meets music this amazing is always a treat.
I did not feel the chemistry between the leads, Yeo Jin-goo's bad acting perhaps? To me it feels like the Hongs tried to recreate the goblin experience, but their writing just did not live up to the task. This is their worst work so far I think. Don't misunderstand it's not bad by any means, but it's like an empty shell compared to Goblin. Even though I think the last episode was pretty good, I just wasn't emotionally invested enough in the characters to really feel the melo, so to say.