One of the recurring themes in DS9 was "can one be a collaborator without moral corruption?" This episode actually does a pretty good job of exploring that by examining one uncorrupted collaborator, Odo - perhaps the only individual who escaped the occupation with his moral standing untarnished.
Within the context of this episode, we discover that maybe it's not possible to avoid corruption. Even good old Odo sentenced innocent men to their deaths - not willfully, of course, but due to banal negligence. It's a great story, and the final revelation is powerful, as is the final scene with Major Kira. (An intentional homage to "Necessary Evil", when the shoe was on the other foot.) Kurtwood Smith nails Odo's mannerisms, something you appreciate even more on repeat viewing.
Revisiting the grim environs of Occupation-era Terok Nor, with its dim lighting and unrelenting grey colours, is also a welcome surprise. But nevertheless, this episode never quite manages to reach classic status. It's not really clear why the other crew members are along - they don't add much (aside from some revelatory scenes with Gul Dukat) aside from being Odo's loyal audience. And unfortunately, we know right away that it's somehow all in Odo's head. Perhaps they could have revealed that at the very end?