I was pretty excited about this show, I was looking forward to something a little more original than what I've been seeing lately. Alas, disappointment followed. I enjoyed some aspects of it, but with the uneven pacing and the glaring plot holes, pretty much all I felt at the end was frustration. As with most everything, there were positives as well as negatives.
LIKED:
1) Shin Hye Sun as Ban Ji Eum - I have loved her in everything I've seen her in. She's real, she's likeable, and she has a firm grasp on her acting ability. She knows when to give us more, as well as when to reign it in, to leave us WANTING more.
2) Kim Shi Ah as the young lady that was Ji Eum in her 18th life. For me, she was the standout in this. She was lovely and poised beyond her years. As I watched her, I felt that she had the knowledge from all her past lives and was somewhat jaded. Kind of like she was forced to act like a child when she was an adult. She was so sweet with her sister and Seo Ha.
3) Cha Chung Hwa as Ji Eum's niece from her 17th life. I love this actress and she brought humor to the role that was welcome.
4) Costuming. I loved the clothes in this, especially everything they put on Ahn Bo Hyun. He must have lost weight for this role, because I've always seen him as being in a sportsman role. He looked great and he wore everything well.
5) OST. Some beautiful music.
6) Cinematography, for the most part, was very good. I especially loved all the colors and movement from her first life. I just wish I hadn't had to see her first life over and over again.
7) I liked how the FL brought all of her skills from her past lives into her current life.
NOT SO MUCH:
1) Who did hair and makeup!?! Her hair was very "Cheese in the Trap" and distracting. Most jarring was the makeup on Ahn Bo Hyun. He looked so white, actually pasty. It looked like someone had slathered on the makeup with a trowel, and the lipstick on him was entirely too obvious and dark. There were multiple times I thought that I was watching a vampire movie, he reminded me of that.
2) I didn't like the forwardness of Ji Eum at all. "let's date". I didn't find it cute or endearing at all. To a certain extent, I felt the same about the 2FL. If someone isn't interested, move on.
3) The murder plot. It started out interesting and ended in a fizzle. What a waste of time!
4) I was never clear on why the guy with the bells was so intent on her remembering her first life, especially since he was there and NOT a good guy.
5) There is a difference between not remembering your previous lives and not remembering the people in your life currently. She didn't have amnesia, for heaven's sake! If she didn't remember them, how did she remember where she used to work? For me, the whole ending was clunky, like they didn't know how to resolve it and wrap everything up.
6) Lack of chemistry between the leads.

So, if asked if I think you should watch, I wouldn't say to run away, but there is a lot of better stuff out there to watch.