Even though I was mildly annoyed that DS9 turned the Terrans into "good" guys (I'm using the term loosely because it's the Mirror Universe), I was glad they made up for it by showing the Mirror Bajorans, Klingons, and Cardassians were all just as bad as the Terrans were when they had their empire. At least as much as was possible to show on '90s syndicated TV meant for family viewing.MU gets an undeserved short shrift in my opinion.
Still, I would've preferred the Dark Mirror version of the 24th Century Mirror Universe over what we actually got. I remember reading that book when I was in high school and I could picture everything in my head, wishing I'd have been able to see it on a TV screen.