"Invasive Procedures" is much better than I remembered - the first time I saw it, I assessed it as just another bit of solid filler. But there's a nice, tense thriller here that explores Dax's relationship with several characters while she actually spends very little time on the screen!
The episode is really Sisko's, and Avery Brooks gives a strong performance. He gets some nice backup from Armin Shimerman and Siddig. The latter in particular benefits from a more serious performance rather than behaving like a fatuous young lieutenant. And in typical DS9 fashion, even though there's a happy ending, there are consequences - a man's obsession may have destroyed him.