Also....
The episode is one of the earliest I remember seeing as a kid. I saw it a few years ago and enjoyed it all over again. Favorite bits: Kirk's sleuthing to figure out what's really going on with the colonists; the creepy movement of the spore plants (and that Sixties bass guitar music!) before we understand what they do; Spock's initial discomfort and aloofness with Kalomi, followed by his giddy romance with her; Kirk being repeatedly flummoxed by his mutinous crew (esp. Spock); his sense of isolation as he finds himself alone on an uncharacteristically - almost shockingly - empty ship; his tragicomic insults of Spock to provoke him; and Spock's final sad goodbye to Kalomi, followed by his, Kirk's and McCoy's classic little conversation on the Bridge at the end.