I fail to see why Kirk can't be given a pass here. After all, Rayna was designed (after repeated failed efforts) by Flint, who was not only a creative genius but had personally witnessed a wider variety of female appeal than anyone who ever lived, had therefore developed the most discriminating taste in women imaginable, and finally succeeded in distilling it all into one female who would be an ideal companion for himself. All we need do is to assume that Kirk would have been attracted to Rayna's physical type (or outer shell, if you will) to believe that of course Kirk would be besotted by her.
It's not that he falls for her. It's that he so ridiculously falls for her, and seems to overlook that people are dying of this disease they need the drug for.
Also that Kirk knows her for only a few hours before he is forgetting about his sick crew and engaging in a hideous throwing match with Flint. I mean, jeez, where's the Kirk Fighting Prowess? That fight was awful, badly motivated and painted Kirk as an emotional cripple - like a 7th grader jealous over his buddy dating a girl he had his eye on.
though, to see that the remastered version of this episode now spells Sorel's end credit as Rayna instead of the original "Reena" (which disagrees with the signs such as "Rayna 16" seen at the end of the third act).
The spelling of the character's name in the credits depends on the print. The original DVDs have it as "Reena", but the earlier Laser Disc / VHS versions have it spelled correctly.
Regarding cool aspects of the third season, I liked the new uniforms (even though a lot of people think they look cheap). The material and the tailoring had a slimming effect on the cast (particularly Shatner, but it also looks like he had some "under garment" aid - although he did obviously lose weight as the season went on). The supporting cast had a lot more to do, probably because guest stars were limited. There was also a change in atmosphere, the show tended to be a little more spooky. I liked that, especially when I watched the show in reruns during the 80's and it was routinely on in the wee hours. Follow that up with a first season Space:1999 rerun and that's some creepy sci-fi.
Weird aliens. Rather than putting a guy in a monster suit, like a Gorn or Mugato, we got a Melkotian, a Tholian and a Medusan. Genuine aliens, totally different forms of life. I'll even give them props for Yarnek in The Savage Curtain, even though it was still a "guy in a rubber rock suit." It worked and was still a pretty cool take on an alien.
The jettisoning of all-out comedy episodes. Granted, Freiberger didn't have the best story sense ever (witness his second season 1999 work), I thought he was right on the money to reject episodes which were full-on comedies. Character humor was great and the cast excelled at it, but I was never a fan of A Piece of the Action or I, Mudd. Tribbles was saved only by some superior gags, but I could have done without it. Second season went too far in that direction. However, Freiberger went too far in the other direction at times, keeping the show dry when it needed a little humor. He changed his tune when he did 1999, but again he was a man of extremes.
A lot of Vulcan lore and fan favorite themes came out of this season. The least popular year gave us IDIC (whatever the profit reasons, it still resonated), Surak and - sadly - the 7 year Pon Farr detail not mentioned in Amok Time.
Finally, I really enjoyed the increased feeling of warmth and friendship between the characters. Everyone was really comfortable in their roles and it came through.
Negatives: unlike a lot of people, I don't have an issue with crappy scripts. Every show has duds. But some of them could have been saved with a little more care and attention to character. This, IMO, was the season where Kirk got his lothario reputation because he was given romantic plots more often. Actually, nearly EVERYONE had a romance and it was ridiculous. McCoy got really shafted: a romance and a disease of the week plot in one episode. Wasting such a talented cast on by the numbers plots, written totally out of character was a shame (some of them came off as were bad fanfic). Scotty had it worst. Jimmy Doohan was given the most awful lines in Lights of Zetar. These romances are meaningless since we know the girl ain't coming back. Others: Spock is beguiled by Droxine for no good reason, telling her very casually about Pon Farr; Chekov morphs from a symbol of youthful freedom to super establishment for one episode; Kirk can't reason with Miranda Jones, he has to dupe her with his manhood (and the fawning everyone does over her is embarrassing); McCoy gets really obnoxious toward Spock in general; Spock becomes really obnoxious in That Which Survives; Janice Lester gets away with way too much crap before Sulu and Chekov finally step in.
YET - for all that - the season has so many entertaining episodes (regardless of quality) that I will never hate it. I may not visit a few episodes all that often, but I enjoy the majority of them. And every season has its stinkers.