I loved the first part start to finish. liked the effects and most of the plot of the second part...HOWEVER....I think they tanked the ending on a MAJOR point. If the Mirror universe captured TOS era tech in the "Enterprise" era, why don't they have at least TNG era tech when Kirk encounters them? After all they would have had the best the Federation could produce a hundred years before our Federation would have had the same level of technology. I know reverse engineering something as complex as the Defiant would take time, but I don't buy it taking that bloody long. For the episode to have worked, the Defiant should have been destroyed at the end.