This episode did a lot of things well. First it gave us a glimpse of Seven of Nine's life as a drone, second it allowed us to meet some of the other "of Nines" and third it continued the theme of exploring individuality versus the collective, and what that individuality is ultimately worth.
The key to this episode is Seven's drive to always strive for perfection, and yet she is confronted with a past decision that was anything but, and that influenced lives beyond her own. Jeri Ryan does a great job of communicating that realization just through facial expressions. Her reactions say much more than words could, and say it more powerfully. That is the essence of great acting.
Side not to these reviews: I'll never understand why some reviewers spend so much time recapping what happened in the episode. I just watched the episode, that's why I'm here. Why do I need a blow by blow plot summary? Or if I didn't watch the episode yet, why would I want to read the specifics of it before watching it and ruin all the surprises?
Live Long and Prosper