I had higher expectations for this drama, so I was slightly disappointed that the plot and the acting didn't quite live up to those. HOWEVER, despite this, I was still engaged with this show and enjoyed it even though it was flawed.
My first criticism is for the plot. I want to preface this by saying that I've never read the comic, so I wasn't influenced in any way by the source material. The issue is that the backstory information that would have been so helpful to understanding what was going on was dribbled out like crumbs on the trail in Hansel and Gretel. I wanted to know more, but the writers would have the characters give some cryptic piece of dialogue and then fail to explain well enough that I felt satisfied as a viewer. The answers came "too little, too late" for many people and I felt somewhat like that myself. I was mostly satisfied with the answers we finally received, but not 100%. I also tend to believe that the budget may have been cut early on. The reason I say so is because the "realm of the gods" was only shown briefly, even though it was splendid. And Ha Baek came through to the human's realm without his powers. He was able to use them twice, and they were marvelous special effects, but then they were not used again. I think they made a good choice to cut the special effects rather than lose production value, but I think they made it a little obvious anyway since the show really could have been something special with a bigger budget.
The acting was fine, but not phenomenal. I think Nam Joo Hyuk was not quite the right choice for Ha Baek. He's adorable, sure. And I've enjoyed his other works. But I don't know that he carried the weight of the role as well as a more experienced actor may have. He wasn't a horrible choice, but I just think they could have done better. On the plus side he was VERY cute. :) And Shin Se Kyung got a lot of criticism for her acting, but I don't think she is a bad actress at all. She played her role fine. The chemistry between the two was hit and miss. Sometimes I thought it was there, and other times, not so much. Im Joo Hwan really knocked it out of the park, though, and was one of the lone actors that really stood out in this show. So much so, that a lot of viewers kept watching for him alone. The other actors were fine. Not anything special, but just fine.
Now, the music on the otherhand, was beautiful. I absolutely loved the track, Glass Bridge. Mesmerizing song! I don't know the names of the others, but the music was lovely. The cinematography was beautiful as well.
I can't say I would re-watch this. Maybe after I read the comic, more of the story will fall into place and I'll understand it better, but that's about it. I do think they ended the show much better than I was expecting, even if it was a bit anticlimactic. This show wasn't horrible by any means, and I hate that so many people gave up on it so quickly. But it was a decent watch even though it didn't live up to its potential. I'm not mad I spent the time watching it.