So, I have realized something, reading through your watch through of all the Star Trek series. I realized that I have not seen all of the TOS episodes. I watched it in syndication growing up on Fox as a kid, and a few tapes we recorded of classic episodes.
So I started watching some episodes I have never seen:
The Ultimate Computer.
No Idea how I never saw this episode. Kirk and Bones psychology conversations about Kirk's feelings for the M5 is great. The resolution to the M5 problem was sort of lame, but I did like how the other captain figured it out.
I love how by the time we get to TNG, the ship is basically using M5 like computer from this episode. Everything is automated and done by the computer that can speak to you in normal conversation.
Spock's Brain.
An interesting little story, formerly advanced aliens using ancient technology to remove Spock's brain to act as a computer controller for the female's underground base. Kirk and crew have some interesting scenes tracking the aliens, and Mccoy gets his iconic, "A child could do it!" scene. Another somewhat lame ending for this episode though given the serious nature of it.