As many already know, Ex-Girlfriend Club had to go through an (uncalled) cut, going from 16 episodes to only 12. Fortunately, this Kdrama didn't seem to suffer much from it and managed to stay true to itself until the very end; so no need to fret about the quality going downhill.
The only valid explanation I see for Ex-Girlfriend Club's low ratings is that it doesn't have any "epic love" nor any "bad-to-the-bone villain". It is simply a heartfelt story with a generous sprinkle of fluff and hilarity, as its OST can corroborate. Although the story is unpretentious, the characters are all layered. Flawed yet lovable, the characters are more than just love interests and whatnot; each of them is his/her own person. The genuineness the characters give off is enhanced by the great acting. The cast did a flawless job, Bun Yo Han was especially shining in this drama. The ones behind the cast wouldn't have been able to find a more perfect fit for Myung Soo, even if they had tried. Not to mention how believable Song Ji Hyo and him were at acting as a couple, they were simply the cutest.
This drama, free of the usual draggy angst, can be watched over and over without losing much of its charm. To put it in a nutshell, Ex-Girlfriend Club is the perfect drama to watch if you want to uplift your current mood.