I think K is a great Anime. Each Character is awesome on it's own and you have to love everyone ( I did and still do).
Sometimes it's hard to follow the story but it is understandable. Maybe you have to watch some parts two times.
But i also have to say that i don't like what happens to two of my favourite characters at the end of the anime. I have to admit i cried really hard ( T.T ). The shouting of the team gave me the rest.
But overall i can say it's really worth to watch and a regret nothing XD