It's one of my favorites. It put the characters in very unusual situations: Kirk living the simple life he'd always fantasized about and getting married, Spock as the brooding commander of the Enterprise. It had a fantastic Gerald Fried score, probably my favorite of his TOS scores. It had the lovely Sabrina Scharf as Miramanee.
If there's one thing I regret about the episode, it's the fact that it introduced the Preservers into Trek lore and established so little about them. Because of that lack of information, the fans have inflated the Preservers into these ridiculously ancient beings of godlike power, and various works of tie-in or fan fiction have confused the Preservers with the 4-billion-year-old First Humanoids from TNG's "The Chase" or credited them with creating everything from the galactic barrier to the Doomsday Machine. But all we know about them from the episode is: they existed as recently as a few hundred years ago, making them modern rather than ancient; they relocated endangered populations, something requiring no technology more advanced than starships; and they were so monumentally inept that they thought it would be a good idea to "protect" an endangered Native American tribe by sticking them in the middle of an asteroid swarm and giving them a single deflector beam that only one person per generation knew how to operate. (Among all the other problems with that, what if the asteroid came in on the opposite side of the planet?) The whole Preserver mythos has been inflated far beyond all reason and evidence. The episode isn't at fault for that, though, except by omission. Leave something blank and people will tend to fill it in with the most extravagant thing they can imagine.
The science is also quite wonky, though that's par for the course. If the Enterprise had two months to divert that asteroid, all they had to do was have a shuttlecraft thrust it sideways for a few hours every day to change its course enough to hit the planet. Or they could've erected a solar sail or spray-painted one face of it white and used light pressure to alter its velocity/trajectory. Heck, just the mass of the Enterprise coasting alongside it for two months would've altered its trajectory gravitationally and it probably would've missed anyway. But I doubt these kinds of deflection strategies had been devised in 1968, though the physics is elementary.
As for the lack of consequences or followup Smiley mentioned, that was par for the course in '60s and '70s television. Many shows had episodes where the heroes fell in love or got married and their lovers died or otherwise went away by the end of the episode, and then those events were never mentioned again. Besides, it's not like the Tarsus IV massacre, the death of Edith Keeler, the death of Sam, or any other defining moments in Jim Kirk's life were ever referenced beyond one episode each. It's not a TOS thing, it's just the way television was written then. Networks wanted to be able to show episodes in any sequence, so continuity was discouraged. Also, the classiest shows in '50s and early '60s TV were anthologies, while continuity was more the province of cheesy soap operas. So even dramas with continuing characters tended to take an anthology approach, rarely or never referencing past events.
