This should be five stars with heinsight because it causes the following chain of events which starts the Dominion war:
1. Obsidian Order weakens and collapses.
2. With the Obsidian Order gone, Central Command loses its grip on the Cardassian people and a popular/disident revolt occurs.
3. The Klingons suspect changeling involvement behind the change in Cardassian government and decide for 'the safety of the Alpha Quadrant' to take over the Cardassian Union.
4. The Federation refuses to help or support the Klingons and sides with the Cardassians.
5. Federation/Klingon war.
6. One disgraced former Gul, Dukat, manages to capture a Klingon bird of prey and engages in his own personal war with the Klingons.
7. Dukat realises he needs allies to defeat the Klingons so he turns to the Dominion.
8. Dukat leads a coup against the Cardassian government, with help from Dominion ships, unites the Cardassian people and military and begins the process of removing all enemies from Cardassian territory.
9. Maquis are wiped out and the Klingons are beating back and out of Cardassian territory. Khitomer accords are signed again by Klingons and Federation.
10. Dominion sends in more ships into the Cardassian Union, Sisko decides to mine the wormhole to stop the Dominion from doing this. War ensues...
It is only thanks to this episode that these events happened, and that's what makes this episode so amazing. The scenes with Garak and Odo are great, the Dominion is finally used to really drive the series forward, and we get a taste of the epic space battles to come.
This is five stars all the way...