I won't make my review unnecessarily lengthy. Obviously you're here for "What's there to like?" Let me answer that for you...
When I started watching Yumi's cells S1 honestly I came for Ahn Bo Hyun. But stayed for the plot. Why? Because it the plot speaks for us. I felt myself in Yumi. She's You, she's us! The emotional rollercoaster we face everyday in our daily life, the hurdles we overcame, the breakups we've been through, the thoughts left unsaid, those overwhelming situations made me laugh, angry, and cry too.
In the mid of S2 I was really confused about the plot. The characters and screenwriters successfully put us into a abyss of contemplation. Which I must say is worth contemplating for!
Ms. Yumi earned my respect. She isn't perfect. She knows how to compromise but she'll never settle for less.
And lastly the beautiful OSTs Ling Ling, Shinning on Your Night both just stole my <3

If you don't want to watch it yes you can skip, no big deal. But if you watch this till the end, I can assure you won't regret it.