Although shown a few episodes in, 'Spectre of the Gun' was the first episode to be produced for the third, final season of the Original Series.
By now, the series had seen many stories that played with various stages from Earth (particularly America)'s past. Some use the infamously over-used "parallel Earth" plot device, and others are to do with alien beings creating the surroundings. This is an example of the latter.
As such, the episode does somewhat feel like a retread of some earlier stories, adding to the 'tired' feel that generally goes with the third season anyway.
It is maybe an obvious setting for an episode, as in many ways the series can be described as a "Western space opera". But the story comes off with mixed results.
Setting-wise it is one of the more interesting of the third (and weakest) of the show's three seasons.
But the episode's main flaw is that it looks so darn cheap. I can go along with the incomplete buildings (apparently a creative decision due to budget limitations), but everything just looks so cheap and flimsy, and not all that nice to look at.
The plot is also mixed. It feels like it should be an awful lot of fun, but winds up as a so-so offering. The concept of Kirk and co. being put into a re-enactment of the Gunfight at the O.K. Corral – in fact, the whole Western setting in general – should be great fun, but things come off as average at best.
It is one of the more interesting and memorable settings of the third season, but that's not really saying much.