I loved 2521. Its easily in my top 3 dramas ever. I cried a lot and i laughed a lot. I even got jealous. The life of the characters seemed so light and free. Everything was perfect untill the last episodes.I love sad endings and i love happy endings. But this was neither. I didnt get the satisfaction of knowing Hee-Do's future and i also didnt get closure for her past. It felt so empty.
This drama is definitely worth watching, but beware the ending is not that good. If youre a person capable of switching your opinions often, my advice is to not read the reviews. You will not be able to enjoy the drama fully.