Unfortunately Wink of an Eye embodies all that is... average about Season 3. It's not a particularly original s.f. idea, since H.G. Wells invented the concept and Wild Wild West used it a year or so previously (and several shows have used it since). In WWW the baroque science concepts kind of allow for it, but in the "harder" s.f. Trek setting, it's just silly.
It's also very representative of Season 3 because the focus is on Kirk and Spock. Compton might have been an interesting character, a Bailey or Styles from the first season, but instead he's some schmuck we've never seen of, disappears before we even find out about him, and shows up only to briefly ignore the captain then come to his aid and die.
So it's the Kirk & Spock show. Kirk gets the girl and Spock plays detective. McCoy gets to whip up a cure in about an hour that has defied the best efforts of the Scalosian scientists over decades, but he doesn't have much to say.
Jason Evers is his dependable stolid "Hey, it's that guy, what's-his-face!" 60s actor. So the show really rests on the shoulders of Kathie Browne, Darren McGavin's wife and another one of those "Hey, it's that woman, what's-her-face!" actresses of the 60s. She gives a great in-depth performance here, and her "At least allow me the dignity..." speech is oddly touching. She varies between puckish, ruthless, and sympathetic, and her reaction when Kirk "adjusts" is well done as well.
Unfortunately despite Mrs. Browne's assets (and William Ware Theiss' costume design), the episode doesn't really overcome the bad karma of the goofy concept. It's watchable, but just barely.