The concept behind this story -- one society supporting itself economically by supplying an addictive substance to another -- is an intriguing one and could have led to a very interesting episode. Unfortunately, we got this one instead.
The writers decided to hammer home an anti-drugs message, worst exemplified by an absolutely agonizing conversation between Tasha and Wesley. (Appropriately, the most agonizing characters during season 1.) Given some of the weird looks Data flashes during this sequence, you have to assume that Brent Spiner is as miserable as the viewer.
Other annoying parts -- the lengthy opening sequence, with some scientific exploration that almost nobody watching this episode would care about; the over-the-top junkie emulation by the characters playing the Onarrans.
Pluses: the conversation between Dr. Crusher and Picard near the end in the turbolift. It's a bunch of nonsense and probably contradicts at least five other discussions of the Prime Directive, but Patrick Stewart delivers it really well in some of his best acting from the first season.
Also, the Brekkans -- particularly the woman -- convey exactly the right smarminess for their role.