I just finished a game, and Sagan never appeared (I was watching for him) I did manage to snag Stephanie Kwolek, and that was enough to put me over the top for a science victory. I had 3 high-production cities and one spaceport. My capital built all the space projects, another city built bombers and fighters, and the other pumped out tanks. Japan was right on the verge of winning and I came from behind for the victory. Gandhi took Wernher von Braun; if Hojo and gotten him, Japan probably would have won.
But what really brought me to this thread was to ask if anyone uses great people as scouts? I played a game as Russia recently, and very early on I was drowning in great artists and musicians. Since they are immortals now, they might be good for scouting out hostile territory. I did use one to clear a barb encampment