Thought it was cool seeing just how much of a difference Roddenberry made to the Space Seed script. After so many chapters devoted to Gene Coon and the magic he was working on the show, it was nice to see Roddenberry prove he still had some good ideas in him as well.
I just love his offhand suggestion that, instead of being common criminals who got shipped off to a penal colony, these people could maybe be dangerous, superhuman tyrants who had ruled much of the Earth. And it wasn't until his final script polish that the name Khan was used, or (according to Justman) that it became the great, streamlined classic it is today.
And I never really thought of it before, but it's clear that with episodes like this, Charlie X, and Balance of Terror that TOS did bottle episodes better than probably any other Trek series. In fact most of the time they don't even feel like bottle episodes (which you definitely can't say about many TNG eps).
He did the same thing in "By Any Other Name" when D.C. Fontana was trying to come-up with a way the 4 Kelvins could take over and keep the entire crew under control. Roddenberry came up with the crew being reduced into those little styrofoam cube things which made the story work. I guess that will be in the next volume.