This drama was such a good surprise for me! I enjoyed it from the beginning to the end. It has been said that the second part of the show is dragging a little bit, but at that point I was so attached to the four main characters that it didn't bother me at all.
I absolutely loved the character of Choi Kang Soo (how can you not?) and I'd like to thank Go Kyung Pyo for existing.
I loved both female leads for the same reason: they were both young women doing everything they can to be independant, despite their families dragging them down / pressuring them. A lot of people seem to think that they were annoying, but I found them courageous and funny, and I enjoyed watching them evolve a lot.
I've had mixed feelings about Oh Jin Gyu as a character, but Kim Sun Ho did such an awesome job at portraying him (his facial expressions are the best) that I ended up loving him too.

The setting around deliverymen is very unusual for a drama, which is one of the reasons why I wanted to watch it in the first place. If you've had that kind of "service industry" job before, you will probably find the characters really relatable and get a lovely kind of "hommage" [to service workers] feel to the drama.

The story is simple, with no big surprises, but that's what I loved about the drama too. The focus is on the characters, their hopes and dreams, rather than on a complexe plotline, which makes it easy to watch.
 It's a simple, yet touching drama about the power of kindness, friendship and persistence. It made me laugh and cry, and left me with really warm, happy feels. I definitely recommend it!