This was a great episode, sans the melodic memory-program somehow embedded in everyone. That was a bit nuBSG for my taste. I'm still interested in where they take it and hopeful that it's not one of these oh-so-clever plot innovations but has a more down-to-earth (ha!) explanation.
Three things stood out to me in this episode, and they were pacing, thoughtful writing, and balanced emotion.
Pacing: Some of my biggest issues with the first two seasons were the breakneck pacing and plot-device clocks and countdowns that made watching the episode stressful but also needlessly so, as you knew they'd "make it out of the pinch somehow." Not the case in this episode, and generally the third season so far. There was a sense of urgency (curing infected people) but no clock. This created a nice suspenseful pressure without all the stress. A+.
Thoughtful writing: Referencing the patterns of history, particularly the dark ages and the innovative thinking that (arguably) ended them, was quite nice. Reminiscent of the thoughtful writing of TNG and latter DS9. No technobabbly plot devices like "Oh humans evolved away from empathy and unless we (Michael) fix this evolutionary error we'll never get the good old Federation back," just, "History's lessons say that even when things are bad for a long time, they can get better, particularly when we shock the system with creativity."
Balanced emotion: I was so happy to see just a bit of very understandable crying this episode. Though I'm not adverse to the new more emotion-friendly Trekverse, particularly in the acknowledgment of PTSD, crying has been far overused the past two seasons as a signal for "Oh wow this is soooo important, guys." Michael's emotional connections with Saru and others in this episode were deep, thoughtful and conveyed mostly through her (non-crying) eyes and expressions. Great acting. Much better balance of emotion and and ease up on the crying crutch.
Overall, I loved it. Gave it a 10. I'm a sucker for these kinds of episodes, though.