If you are looking at this drama after maybe watching the other versions of this drama then i can assure you that this is the most intense, the most heart-wrenching and most love-able drama out of them all. There wasn't anything wrong with the drama, everything was perfect: the acting, the story line, the actors and actresses. The ending was also great.
NOTE: just to remind you, this is only season 1, there is a season 2 and then after season 2 there is even a movie to finish it all off. So be prepared for a long ride of this drama.