As an episode on its own, I thought it was a very well directed episode. Even though they did a bad job with getting the audience to sympathize with the Devil Girl, I still felt sympathy for her, but maybe I'm just a softie. Nikki needs to stop being such a "bad-ass" and show some weakness, but I suppose her taking up the case of the dead hooker is a way of showing that she has a weakness. Overall, even though they could have used a lot more math in this episode, it was still a good one.
Also, the crossing of a former character with Don made me very excited for the ending of this season, which I hear is the series finale.