Hated this episode fifty years ago, love it today. As a little kid I was freaked out by the scary silver eyes, but also I didn't like the unfamiliar uniforms and the unfamiliar faces or the way Kirk and Spock barely seem to know each other.
Today all the weak points seem like strong points to me. This is the one episode where Kirk and Spock actually relate like an earth man and an alien, with a wary distrust that gradually changes to grudging respect. I could do without Nimoy's SHOUTING his dialogue, though. "FULL power!"
The fact that the villain is an old friend of Kirk's makes it a lot more powerful, though they repeated this trope a little too often in later episodes. But Gary Lockwood really has a very Kirk like quality, and that strengthens the story as well as adding some unintentional humor. ("I'm not JOKING, Lee!")
But the best thing about this episode by far is Sally Kellerman, at the very height of her beauty, playing a woman who has dignity, integrity, empathy, and compassion -- and who falls head over heels for a man destined to destroy her. It's silly science fiction stuff, but when she cries out "a mutated man could also be a *WONDERFUL* thing" you are seeing right into her heart and soul, seeing how she's fallen and she doesn't even know it.
Oh, and don't forget pretty little Yeoman Smith -- I mean Jones! I really wish she had become a series regular.
