This lengthy drama is well damn worth it. Even though it is long, it is not boring at all (i binged watched the 51 episodes in a week or so).
But the length of it is actually really nice, because the characters are very well developed, to the point that they are not stuck in their general theme and evolve alongside the story.
You follow their fails, success, concessions, and change of character throughout this wonderful journey.
I'd say that the actors are all really really good, except for Joo Jin Mo, who has a more tight role to play (he still does a honourable job).
The main character is exceptional : Ha Ji Won plays her role in a very convincing manner and her character is so cool because of her.
I'm so baffled by the whole Empress Ki experience, that i'll most likely rewatch this favorite drama of mine.