Everything about this episode was just perfect. The writing, the acting, the direction.
So many subtle things made it even more effective, like Sisko slowly taking off his uniform as he undresses his feelings. Or how Vreenak first thought the kali fel was only a good 'approximation', until Sisko made even stronger points and he takes another sip and says that for a moment he thought it was the real deal, signaling he was becoming a bit more convinced.
Or the final scene with Garak... notice as Garak was explaining why he thought Sisko came to him, he started off over one of Sisko's shoulders and suddenly, as he explains the cost in lives and self respect and let his conscience be soothed that it was to save the quadrant, he is on the other shoulder. Very much like an angel and a devil on Sisko's shoulders, and Garak essentially played both parts.
This truly is an episode that should be broken down in film school and each part used as a teachable session.