This is not the greatest episode of Star Trek, but I like it because it really has most of the classic Star Trek themes and situations. There's a landing party that gets mixed up with natives, and to save his crew Kirk has to take drastic steps to alter the course of their civilization. There's a lot of romance in the air, (though interestingly, no romance for Kirk.) There's plenty of time for Spock and McCoy to debate concepts like free will, change, and material comfort versus freedom. And of course, several red-shirt crew members are killed along the way. There's a big fight and plenty of storms and lightning.
As other reviewers have pointed out, this episode deals in themes that are handled much better in later episodes like "A Private Little War" and "The Paradise Syndrome." But this one is still a lot of fun -- have to love the albino Polynesians learning how to smash melons, and the stunning blonde showing off her long legs in those devastating karate kicks!