I'll start with the reason this show got the high score that it did. Yoon Hyun Min! I just finished watching him in Falling for Innocence and I was looking for something that he would play the romantic lead in. He's been in numerous shows that are not romances, but since I'm usually pretty much all about the romance, those shows were not what I was looking for. He was excellent in this. Playing cold, rich, damaged Nam Do and Holo, the hologram that inexplicably develops AI, I felt that he was able to display a range of emotions, often side-by-side. When he was Nam Do, you could feel his drive, his brilliance, and his loneliness. Watching him roam the workplace in the middle of the night was just sad to watch. He had every convenience available to him, but he was always alone. Then, as Holo, he was boyish, charming, caring, and as Holo he kept evolving as he developed AI characteristics. Hyun Min has a very interesting look about him. His features are sharp, his look is intense, and he's, of course, handsome. But I have to say I'm more fascinated with his acting than the way he looks. Because I enjoyed the parts he played in this,, I totally would have rated this show higher if not for:

STORY: Every K-drama trope in the book is in this one! It starts out really strong, but then becomes a mess about halfway through. The storyline continued to get more complicated and unnecessarily implausible. How they dealt with Holo toward the end was very emotional and touching. Obligatory time jump at the end (yet another trope) and the last scene was very cute, but the overall ending was unsatisfactory to me, mostly because:
ROMANCE: I felt that this show was too light on romance and it wasn't fully fleshed out. Why did Nam Do like So Yeon? That was a mystery to me. I felt like she was the first girl he ever talked to so, of course, he had to like her. A couple of really bad/accidental kisses. Later on there were some good kisses, but I was wishing that Nam Do and So Yeon's relationship would have been developed more completely.
CHARACTERS: So Yeon. Go Sung Hee did a good job in this show. I'm used to seeing her as the kind of bitchy secondary character, so it was nice to see her as the lead. However, So Yeon spent entirely too much time crying/sobbing/drinking. She was pitiful. And her liking Holo - that just didn't work for me. I'm glad they addressed the issue that she liked him because it was safe and she wouldn't get hurt like if she was dating a real person, but it just didn't feel real to me. I enjoyed the other characters in the show - the secondary couple, Nam Do's co-workers, the policeman and his sidekick.

TECHNOLOGY: The technology addressed, and the cinematography were both really good.
MUSIC: Went well with the show. Nothing really stood out to me, but it wasn't distracting.
Random thought: I wonder why they have to translate the curse words in these shows. Couldn't they just use another word, rather than cursing?

OVERALL: Definitely worth watching, but it wasn't one of my favorites.