I seen somebody on Facebook comment yesterday that this episode is "a little too much like the Mirror Universe" for their liking, which to me feels like it's completely missing the point. Visually, yes, the episode suggests a darker, grim take. But these are not evil versions of the crew we know. In fact, what makes the episode so perfect is that the characters are spot on. Everyone is recognisably themselves, just 'for want of a nail'. Underneath his brusque realism of the horrors of the war, Picard still has his optimism, it's just been buried. Indeed, I like to believe it's this idealism that things could be better that is what drives him to send the past Enterprise back.
One of my favourite things about the episode is the way it suggests a completely different paradigm, not with big massive things, but with subtle ones: the noticeable friction between Riker and Picard, or the obs lounge being a 'war room' with tactical maps instead of a conference room with plush chairs (symbolically, replacing the regular TNG's method of 'we can always talk it out' with 'standing to fight is our only option'). Or the subversion of light: the usually bright bridge, ready room, etc are ominously dark, claustrophobic command centres, evoking a utilitarian war ship, while Ten Forward, typically a place with relaxed mood lighting, is instead floodlit and looks more like a mess hall. This isn't the mirror universe, with cartoon-like replacements of the regular characters, it's just a recognisably inside-out version of the Star Trek we know. The episode masterfully sketches out a whole alternative series of history in broad strokes, which is why I think it's still compelling 30 years later. I've never tired of hypothesizing how things came to be so different, and yet still so much the same.
If I have one criticism, it's that I've always felt Denise Crosby's character is still... stuck in Season One, somehow. While the rest of the actors have had three years to get the feel of their characters and there has been some degrees of character growth in all of them, Crosby unfortunately comes back into the ensemble without that benefit. Yes, she's undeniably better written, but her presence doesn't feel like it "gells" with where all the other actors have come in three seasons in the development of their characters, and their bond as a team. She comes back as something of an outsider, although, perhaps I'm being a little harsh, as that degree of her being somewhat outside of things helps to underline just how 'wrong' (to paraphrase Guinan) it is that Tasha is even here at all.
