Ji Pyeong and Won In Jae should have had a better ending than what was given to them. They had the best character development and it was disappointing that the show ended the way it did. Obviously, Ji Pyeong won people's heart with how much he went through to achieve success. In Jae might have had a life of luxury but she worked hard to get where she was with her step father's company. Both of them deserve better. Seo Dal Mi character did mature along the way. Nam Do San in my opinion is the most selfish character in the show. He had parents who provided and supported him, he's smart and good looking, all he had to do was push himself to succeed yet he is so hang up with one mistake that he is the one ruining his life. If Ji Pyeong had never entered his life and change its course, he would have been stuck with his dead end business. Dal Mi and Do San having their HEA just didn't sense.
As for the story, it started out well, building the start up company and tackling the hiccups that came along the way, but after the time jump, the premise of the story got lost. The success just happened and the problems were just glossed over. I won't rewatch the show. I would still recommend it, just don't expect a thought provoking story.