Ahhhhh, this show did something awful to me. I'm sniffling here after that finale... Don't make me talk about it...

Story (8.0):
Wow, I really loved parts of this story. One of my favorite dramas is Healer, and some of it reminded me of that (and City Hunter, etc) and really a lot of the action was very good.
HOWEVER; The Finale pretty much ruined everything for me. Yes, there were other things that detracted from the overall story: there could have been a better romantic story line (like seriously wth I love action but give us some mc together time); too much making us guess who's actually good (come on I like trying to figure out mysteries, but you can't have everybody be an undercover cop). And the latter half of the story, while still packed with action, was just not as good as the first half.
Despite these, I could have given the story a 10. If it weren't for the finale.
To be honest, I was thinking of giving the drama an overalla 10 at episode 19, even though it wasn't as perfect to me as my other ten ratings.
But that finale. Nevermind that they try to crush your heart and soul.
It's too abrupt. That could be forgiven, if it were logical abrupt. Like seriously did you think you could just kill a few people have a random heart to heart scene between characters who weren't developed enough and then give us a few hallucinations to make us happy? Bwah, I want to kill the writers.
Talking about developed characters... Yes, Soo Min and Ji Hyun were done okay, but honestly they were pretty undercooked.
This doesn't mean the character development was bad. I would almost rate characters a 10 just with Safari, Lee Jin Suk and Jung Si Hyun alone. They were awesome. I really liked Lee Jin Suk's character and seeing the heartbreak towards the end she went through... It was very well developed and this will definitely cross over to the acting section.
They were done so well however, that Soo Min, our supposed main female lead, felt stale. Honestly, she didn't develop all that much...

Acting/Cast (9.5):
I'd like to give this a 10 because there were quite a few actors in here who just knocked it out of the ballpark, seriously. Lee Jin Suk, Jung Si Hyun, Safari, the actors for them did a wonderful job. There weren't any actors I seriously thought were bad at acting, but even Soo Min felt a bit underplayed, albeit I think this is mostly because her character wasn't focused on as much as I wanted.

Music (8.0):
It was good. It wasn't anything I'm downloading though. I'd heard a couple people talking about how they really liked it, but honestly nothing sticks with me. I don't care if it is a good instrumental track or a catchy ballad, I need something that I want to listen to more than once to make me rate highly on a soundtrack. I'm thinking things like Empress Ki theme, Sensory Couple theme, main ballad in Behind Your Smile, etc. This was good but nothing that held my attention after the drama was over.

Rewatch Value (8.0):
There are a lot of stuff especially towards the middle that I really enjoyed. However, I will never ever watch that finale again. Kill me now.

Overall (8.0):
I loved a lot of this show, and there are other shows I've given an 8.0 rating that I loved a whole lot less.
I probably would have given at least a 9.0 if they had given us a decent and fulfilling ending. And I'm not talking Hollywood. Kill anyone you like, just make it meaningful please.
Give me a few months--maybe make it a year--and I'll probably find myself rewatching my favorite parts. But I doubt I'll ever do a whole rewatch.
Simultaneously brilliantly amazing and disappointing.
Give it a shot and stop at episode 19.