I also enjoyed this episode.
I liked that after the previous two episodes having simpler stories this time they went in for a more complex, hard sci-fi story. It also managed to be a logical continuation of "The Tholian Web" without disrupting any of the Mirror Universe canon.
I likewise agree that the case has melded nicely and you can tell that with a stable cast they have managed to capture a sense of cameraderie. No weak performances either.
Nice work.