The episode kinda sets the course for the rest of the war; it indicates that the Dominion are currently in the dominant position, that the Romulans will enter the war on the side of the Federation, and that the Cardassians will eventually revolt against Dominion rule. It's interesting that the writers laid out the broad strokes of the war in this episode for us all to see, but they still had those events play out in unexpected and exciting ways.
In hindsight, it also helps make the Jack Pack more convincing. While they were wrong on the "having to surrender" front, the fact that their predictions regarding the war are generally accurate helps, on second viewing, convince me that they must have been genuinely good at what they do. So I'm more able to buy the idea that Bashir accepts their recommendation, now that I know they're generally on the right track.
Oh, and I like the Jack Pack, too. I'm glad they returned in season 7.