Memory Alpha has a summary here.
This is not the worst of the Mirror Universe episodes, actually. The fact that M!Bareil and the Intendant pop into our universe prevents the writers from going overboard with the cheesy, sadomasochistic sex play. (Although -- the Intendant falls sexily when Bareil stuns her. Did you notice that? I did, and I cracked up laughing.) Still, the entire story is very -- unfinished. We hear that the Intendant is planning to rebel against the Alliance - which is an interesting new wrinkle - but (here at least) we never find out why. The writers simply don't make the effort to explain it. Moreover, unless I'm forgetting something, the writers also forgot to mention how the Intendant found out about the Orbs. Do the Prophets have a presence on M!Bajor as well?
Lastly - and most importantly - I will never understand the writers' curious obsession with bringing back old lovers (or, rather, the M!versions of them). Bareil died in season three, people. Since then, Kira has dated (and dumped) Prime Minister Shakaar and has learned that her best friend has romantic feelings for her. I agree with Nana Visitor: I think Kira's over Bareil. I mean, I'm sure she still misses him occasionally - just as Sisko misses Jennifer - but not so much that she'd fall for his doppelganger.
This script is not entirely heinous, but frustratingly, it tends to skim the surface instead of exploring the depths.
Weirdly enough, Philip Anglim is more animated here than he ever was as our Bareil -- and Nana Visitor's performance as the Intendant is almost subtle.
There's nothing to report on this front.