Airing in June of 1969, "Turnabout Intruder" was aired as an afterthought (as TV shows typically bowed out during March and April back then), and in some ways was produced as an afterthought: the climax of this episode seems excessively rushed, robbing an interesting premise of the time and care it deserved.
Instead, the series' only episode focused primarily on gender issues comes across as an impediment to the wrap party. Add this to the fact that Dr. Lester, disturbed as she might be, might actually be *right* about the Starfleet of the Original Series, and you have a less-than- fitting end to a landmark television program.
This isn't to say that the entire episode is bad: Sandra Smith turns in an excellent performance as Dr. Lester, and more importantly, Kirk-in-Lester's body, better than Shatner's rushed take as Lester-in-Kirk's body. Also, there are numerous references (primarily by Smith as Kirk) to previous episodes, a nice touch in this, the final episode of the series.
What probably disturbs me the most about this episode is how poorly it has aged since I first saw it in the mid '80s. While Janice Lester is clearly off her rocker, the direction seems uncharacteristically harsh towards her. After all, we've seen a number of captains (and a few commodores, as well as a collection of admirals and high-ranking civilians) on Star Trek, and other than Chris Pike, Matt Decker, Garth, and Bob Wesley, they're generally a fairly pathetic bunch (and even Decker and Garth were all too human), validating Lester's claim that she could also do the job just as well, if not better. It's almost like the rare episodes of The Twilight Zone where the good characters are punished-while there might be a "good" ending, the viewer is ultimately cheated, as justice has clearly not been served.
But, then again, maybe that's the point-viewers in 1969 were clearly not content with the end of Trek, and they turned a failed TV show into a cultural icon.