This is a very well-written show with well-developed characters. None of the characters are shown to be particularly good or particularly bad - but as human beings, which is something I greatly appreciate as a writer and avid drama-watcher. The realistic themes covered here will definitely get the viewer to think long and hard about our societal framework and how that can either help or hinder our happiness.
Another thing I like is the acting of the main four. Though all of them are subtle with their emotions, they still form distinct personalities which make for great performances overall. Understated acting is perhaps one of the hardest types of acting to accomplish, so I believe the lead actors did a superb job with their characters, being neither overdramatic nor wooden.
A warning for those who want a happy ending: you will be sorely disappointed. The ending is an unconventional one which feels like a missed target. Especially with the emotionally-draining situations the characters are often stuck in, not experiencing even one moment of true happiness, the ending feels like somewhat of a waste, especially for viewers like me who watched the drama as it aired. If you decide to watch this show, be careful to not get too emotionally invested in the main characters as I did.
To close, I would recommend this to anyone who enjoys rich character development and unpredictable, yet realistic outcomes. The best part of this show is how incredibly human the characters are, which is something I believe needs to be shown more in movies and TV.