Overall, I really, really enjoyed watching this series. I cried when the scenes were packed with emotion. I laughed through the comedic relief. And I found myself annoyed at all of the things that were left unsaid, which made it feel closer to real life. I wish it didn't end so soon, or in such a neutral way, but I can appreciate the sort of "use your imagination" efforts.
Also, I can understand why some people feel like the leads have no chemistry, but personally, I don't agree. If anything, the differences in passion between the two added to the charm of this 30-year longing. Jung Hae-in absolutely killed this role. In ep.9, he was so good that it made me think he loves her in real life.
It's a 4/5 for me, solely because I think some parts weren't necessary. Otherwise, I would definitely watch again. I wonder if I'd have the same reactions as the first time.