This is a pretty good one, most notably famous for having Jonathon Frakes guest star as Riker. The twist that he's not actually Will Riker is absolutely fantastic if you go into this without knowing (and the beard-removing moment is kind of funny in its epicness).
For all the good stuff, I do find this episode slightly disjointed. It's split into two very distinct parts, with the early acts being a nice ensemble piece on board the station, and then changing into something very different once Riker is on board the Defiant and Sisko is on Cardassia.
Those Cardassia scene are quite fantastic, though. Sisko is especially great and demonstrates his excellent tactical skills, as well as his ability to find a way to get what he needs. The scenes between him and Dukat are quite electric, thanks again in no small part to how great Marc Alaimo is in the role. The bonding moment they share over both being fathers is a real highlight - thought, a part of me does wonder how truthful Dukat was being. Given all that we discover later about his character, this doesn't quite ring true and feels more like a manipulation. However, I like to think that at this point in the series, the writers wanted to make him genuine, so it's nice.
The stuff on board the Defiant is a bit less enticing, and I find that the episode sort of slows to a crawl as it goes on. Jonathon Frakes' charm helps it, but there's a lot of staring at screens and characters trying to persuade each other to get through. Kira has some great dialogue, fortunately.
First mention of quantum torpedoes, and a nice mystery being set up about what's going on in the Orias system. It's a real shame that the Thomas Riker storyline was never followed up on screen, but it does get some continuation in the relaunch novels.