FUTRE EDIT: I recently re-watched this drama and now feel compelled to come back to my old review and make amendments, as I made some criticisms that I simply don't agree with anymore.

Original Review (now with amendments):
I'm gonna give you one suggestion before you start this drama. Disregard everything about Do Min Ik being a face genius. It's superfluous information that has no bearing on the overall story, and you'll enjoy the drama better if you just ignore it.
EDIT: I completely renounce this suggestion. While there are still some issues with this part of the plot, I don't think him being a face genius at the start is as big of a problem to the story as I once did. I address said issues a little further down in my original review. :FINISH EDIT

As for the rest of this drama, it has an old-school style filled with small, but important, twists on a classic formula. A male lead who's not really a jerk, just starts off a little thoughtless then quickly becomes the cutest puppy you've ever seen (and I mean Quikly). A female lead who's a candy but not, who stands up for herself repeatedly and doesn't let anyone push her around and is very proactive in her own life. The use of disability(ies) in a way that is thoughtful and kind, even if not very accurate (looking at you, face blindness), and that isn't used as a plot device only to be reversed later (ie. not giving characters disabilities only to take them back at the end in order to achieve a 'happy ending').
EDIT: I STAND BY EVERYTHING IN THIS PARAGRAPH. :FINISH EDIT

There's an office plot outside of the romance, but that's gonna be really hit or miss for a lot of people, and probably more of a miss for most. It's not a typical office plot, in my opinion, and I really appreciate where the writers were trying to go with it, but it does have some glaring flaws that keep it from being as compelling as it could have been.
EDIT: I really liked the office plot the second time around. It doesn't go the direction you expect it to (I suspect because one of the actresses playing one of the secretaries central to this plot had to leave the drama due to a family scandal and this required changing the storyline unexpectedly), but I actually like where it ended up going. It's not super high stakes or exciting or intriguing, but it's very realistic and conveys a very strong message. :FINISH EDIT

The two main problems with this drama though are going to be this:

1) Making Do Min Ik a 'face genius' worked against them when they took away his ability to recognize faces, as he should have had no real trouble recognizing the people around him via their voices, mannerisms, way of dress, etc. (as is implied he was very good at when he was a 'face genius'). Yet he can't recognize any of these things about people, and there's no reason given as to why, which makes you strongly question just how much of a 'face genius' he was before. This is why I said to completely disregard this part of the plot as it's unnecessary and you'll enjoy the story more without it.
EDIT: I mostly stand by this. It doesn't make sense that he was so incredibly good at reading people and then when he lost his ability to see faces, he lost everything else as well. At the very least, he should have been able to recognize people's voices. I can recognize my parents' coughs and sighs and sneezes when they're on different aisles of the grocery story. Surely, he could have recognized people's voices. :FINISH EDIT

2) People are tired of dramas where the main conflict is dragged out longer than necessary, and this drama definitely makes you feel like the main conflict is being dragged on longer than necessary and can make you really dislike the female lead even though you clearly aren't meant to. (I never disliked her as the lie itself never upset me to the level it did everyone else, but I definitely felt the frustration many felt over her not ending it sooner than she did.) But once you get past this part of the story, and the writers finally give you an explanation for some things, you do understand why they chose to go this route, and it makes a lot of sense.
EDIT: Again, I mostly stand by this, but I also felt a stronger empathy and understanding for Gal Hee this time around. Truthfully, some of the blame should be on Veronica as well, as her way of punishing Gal Hee for deceiving Do Min Ik...was to make her deceive him some more. She should have been held at least partially responsible for that. And even though the lie goes on overlong, I also think it was consistently well-utilized. There aren't any scenes where I felt like 'This is unnecessary. This harms the drama/the story.' The conflict I experienced was that I understood and appreciated the decisions the writers were making with the lie while also knowing and anticipating and being already heartbroken that Do Min Ik was going to be gutted when he found out. And he was. :FINISH EDIT

What I would have liked to see in this drama:

1) Gal Hee's mom should have been a central character from the beginning. The drama starts off with mom playing a more central role in the early episodes as a sort of voice of wisdom to Gal Hee, but then she sort of disappears for awhile for no explainable reason. She starts popping up again in the second half to have little, private conversations with Gal Hee about things, and it adds So much to the story as you get to see into Gal Hee's mindset and why she does the things she does. The first half would have greatly benefitted from more of this, and I think people's anger at Gal Hee's character would have been cooled by it.
EDIT: I don't know what I was on about. Mom was actually very well-utilized throughout the story, and I don't know why I remembered her only showing up toward the beginning and the second half. I'm also not sure if the story would work as well if mom showed up more often. I liked her a lot, but it probably worked better for her to pop in periodically rather than every, or every other, episode. :FINISH EDIT

2) I don't mind that Do Min Ik couldn't tell that Gal Hee and 'Veronica' were the same person. The explanation we get later on as to why works for me. There just needed to be more insight early on into what was going through Do Min Ik's mind to help us understand why he never recognizes how similar Gal Hee and 'Veronica' are to one another and why he has so much trouble choosing between them. It would have gone a long way to easing the frustration a lot of viewers felt over his not being able to figure it out.
EDIT: I agree. :FINISH EDIT

And that's ultimately where the split is going to be in this drama. Either you're going to be frustrated with Gal Hee for not ending the lie sooner or you're going to be frustrated with Do Min Ik for not recognizing they're same person. But at least for my part, I don't feel like either of these things should deter anyone from watching this drama. I fully admit that my rating for this drama is based purely on my enjoyment of it and not it's flaws. Despite the flaws and some frustration in the middle bit, I thoroughly enjoyed this drama. It's fluffy and lighthearted and not meant to be taken too seriously. The writers know exactly what kind of story they're trying to write, and they don't try to be anything they're not. At the same time, they managed to take an old, tired formula and make it new and refreshing and full of little twists here and there and filled with characters you can't help but fall in love with. (You will love Do Min Ik. You just will.) It also has possibly one of the greatest final scenes in all of dramadom. Literally. That. Was. The. Moment. To. End. The. Drama. On. That last scene….was perfection.
EDIT: My rating for this drama is because this drama is wonderful, and the flaws are not nearly as large as I once thought, and the emotional heart of this story is compelling and strong, and the leads are incredibly sweet together, and I stand by this statement, Dang It. :FINISH EDIT

I highly recommend this. It's too cute not to.
EDIT: HECK YEAH, I DO! :FINISH EDIT