So, first things first, this is NOT a show you can watch casually paying little attention to the details. If you can however, pull out an hour at a time giving full concentration, you'll appreciate the sheer brilliance of its storyline and it's characters.
Every emotion of every character in every scene appears original and heartfelt. The show gives you a chance to witness the development of each character and justifies their actions based on their own traumatic experiences. The ideas expressed through the show and the execution of the entire plot is simply unparalleled.
The way that the evolution of each character is closely tied to every action and it's consequence is different from anything I've ever seen before. Lastly the ending ties up every aspect of the story beautifully and is the first time anything goes right, digressing from the theme of tragedy in the series, making it the most well written and satisfying conclusion to a masterpiece of a show.