Plectrum

I agree it's worth watching. The only thing for me is there's such a vast difference in the pacing of difference scenes in the show that the show is almost at odds with itself. In normal schoolgirl Saya's life are some very very slow scenes about Saya's family life and her struggle to overcome her weaknesses and find her place in the world as a woman. This kind of pacing can extend for several episodes in length without much real conflict--or at least it seemed that way when I watched it. In the scenes where Saya is a red-eyed, sword-wielding killer, the pacing is very fast, with high octane sword fights, decapitation of monsters, gory murders and generally a lot of life or death situations. For somebody who finds the drama of Saya's family life interesting, the fast paced scenes are likely to seem very gory and at odds with the placidness of the rest of the story. For somebody who likes the red-eyed Saya best, the slow scenes are likely to seem really slow. I fall into the latter category and personally I was bored out of my mind by more than a few episodes of Blood+. I view Riku and Kai more as obstacles for the show than as integral parts of Saya's life drama. That said, I still think the show is still worth suffering through the slow parts (if you're like me) to get to the awesome parts because the slow parts do add meaning to the fight scenes anyway and the overall story is quite good.