For me "The Enemy Within" is the first real miss.
Despite Shatner's great performance this episode is just kind of off.
There are too many inconsistency's.
They can't use the shuttlecraft?
Why not beam down some kind of shelter? Or Fire wood?
Why such a wide variation in the planets day/night temperature?
How/why does the transporter beam good kirk up, and then wait
to materialize bad kirk?
How does a repaired transporter "recombine" the 2 Kirks?
There are also the goofs with the scratch's on Kirks face switching sides and
Kirks command insignia reappearing in some shots.
Some of the good:
A good episode for Sulu
The Vulcan neck pinch
Overall I give it a 5
I love the episode, its a great piece of Trek, but hey, there are so many inconsistencies in the story as you`ve pointed out,