Although not bottom-of-the-barrel, this is generally one of my lesser favourite episodes.
It is mostly a comedy, but beyond the flamboyant Mudd himself (more of him in a moment), it's not really laugh-out-loud material, and not a patch on some of 'Star Trek's other more light-hearted episodes.
The presentation of the women, who survive on their looks, is very dated, and works against the episode. The theme of the mail-order brides could have been cutting edge and ahead of its time, but sadly things don't rise much beyond the basic and predictable.
The best thing about the episode is undoubtedly Roger C. Carmel as the roguish intergalactic conman Harcourt Fenton "Harry" Mudd. The character was popular enough to return in the second season episode "I, Mudd", as well as 'The Animated Series' episode "Mudd's Passion".
The plot of Mudd having his women on drugs has darker implications than the episode presents; it is seen on-screen as merely to make his "cargo" look better and raise a higher price; and Mudd is presented more as a scoundrel than the drug-peddling pimp that he might have been.
I also wasn't convinced in the whole "believe in yourself" resolution of the story.
Other than that, the plot is pretty simplistic, and, in places, very slightly dull. It could have done with a separate b-plot to beef things up a bit (these didn't really become common until 'The Next Generation').
Don't get me wrong, this isn't bottom-of-the-barrel, and it does very much end up as a colourful, kitsch example of the 1960 (well, it's set in the future, but you get what I mean). But this episode just sadly doesn't do that much for me.