It also stands as one of the most credible and artfully constructed period pieces in Star Trek history. The use of jazz music throughout and the attention given to every detail of set decoration and costume design makes it among the most immersive and believable of such Trek stories.
The episode is also an example of Star Trek taking on a social issue directly. Where many Trek stories--especially in the Original Series, but throughout them all--deal with earth-bound, contemporary themes by means of metaphor and symbolism, "Far Beyond the Stars" plants us right in the midst of racial tensions in 1950s America.
Of course, this is still something of an indirect storytelling method, using a period in our past to ask us to think seriously about issues that remain of contemporary importance. By looking at racism in a more stark, but less current context, the audience is able to examine current racial conflicts within a larger context. Still, while race is an incredibly important topic in this episode, it is surely only a part of its larger, and core idea.
For my exploration of that idea, read my blog post at Reel World Theology, written as part of their annual Trektember event!