This show started out great! I was at the end of episode two, at which time I had just a couple of issues, and I texted a friend and said that this was the type of show that I could lose sleep over just to binge watch. Unfortunately, that feeling didn't last much longer. I spent a lot of time angry with the writers as I watched this, and I never felt like they redeemed themselves.

I'll start with my positives:
Acting - all of the acting was good, but especially Soo Hyun Jin as Oh Soo Jae. Oh, my goodness, I hated her at the beginning. I did wonder why that, in order for a woman to be strong and successful, they have to be a complete B***ch, but the brief times of humanity were understated and suited her personality completely. The writers did a good job here, in giving us back story following some of her worst moments that would clarify what actually happened. Heo Joon Ho as Choi Tae Gook was amazing. He was the embodiment of evil. I don't like watching this type of character, especially since he doesn't even pretend to be a good guy, but he just drew me in. Then there is Bae In Hyuk as Choi Yoon Sang - he fascinates me. I've seen him in numerous things, and there's something about that little lisp he has... and, finally, Han Joo Hyun as Choi Jae Yi - what a precious little girl!
Found families - between Gong Chan and his hyungs, and the law school students working together, I enjoyed these relationships. I just wish they were developed better/further.

Now for the negatives: SPOILERS!)
1) For me the biggest elephant in the room - why the heck did they use two different actors for the male lead?!?! The younger version of Gong Chan looked older than the Hwang In Youp version! They didn't resemble each other in any way. I kept waiting, throughout the show, for the writers to give us an explanation, but that never happened. It actually seemed like one actor dropped out and Hwang In Youp stepped in at the last minute. I know that's not the case, but that's what it looked like to me. When Oh Soo Jae says to herself, "Why didn't I recognize him?"
2) Romance - They would have been better off leaving the romance out of this show, for many reasons. First, the age disparity - perhaps not so much in chronological age, but in emotional age. He was like a puppy chasing after her, and he seemed more like a high school student than a college student. Plus, the fact that she was a lawyer settled in her career already. And he liked her because she believed in him? That's it? The fact that he kept telling her she was "cool" cemented his immaturity. We had a few brief scenes with them together as a couple. The rest of the time he was either saving her, trying to save her, or holding her while she cried. This was definitely not a give and take relationship. I didn't ship them at all as a couple, to be honest. He called her "Professor" throughout the entire show. At some point in time, if you are truly in a relationship, you use first names!
I loved watching Hwang In Youp, but his character was not well-written.
3) Plethora of bad guys/evil characters. Probably a ratio of more than 2:1. There were so many names to keep straight (especially all the people in the same families), from the past and in the present. Each seemed more evil than the last. The number of things that these people got away with was astounding - multiple people get away with murder (literally), yet they want to draw attention to themselves by bringing her before a disciplinary committee?! And for all the evil done, minimal consequences.
4) Unnecessarily complicated storylines. It seemed like every few minutes they introduced a new character to confuse us. I lost count of the number of storylines that I was trying to keep track of.
5) The direction they took Bae In Hyuk's character Choi Yoon Sang - this one was hard for me to swallow. He likes her, he specifically mentions that he has finally found, in Gong Chan, someone that he can be friends with, yet he threatens pouts and blindsides these characters!? With so many bad guys, I would have much preferred he remain a constant in the ever-changing lives of the two main leads.
6) Too much drinking. Is no one able to solve problems without binge drinking?
7) Vulgar language. I don't know if these were actually the words or just due to the translators, but I don't find bad language necessary.
8) "Stupid heroine" moments. Your office has been broken into, yet you go on in. The guy that attacked you in said office runs out, but rather than leave you go to the roof?!?! What was that about!? Someone calls you to meet him at a deserted place late at night and you go by yourself. Apparently, she's never watched any type of horror film - the stupid characters are usually the first to die.
9) Wow, the labs were doing a booming business in this show. The number of paternity tests and DNA tests that were being run were ridiculous. And finding out that Choi Jae Yi was actually her daughter? I saw it coming from a mile away, and it really made me mad. It just seemed like something else to throw into this mess of a story.
Which brings me to -
10) The truck of doom. I can't even begin to tell you how much I hated this. It was just mean and could have been avoided completely if the stupid paternity storyline hadn't been introduced in the first place.

So, upon reflection, for me, the writing was where the problems were. I'd say, if you have a high tolerance for things that are implausible, watch this show for the excellent acting.