You know, honestly, I can't dislike Through The Looking Glass. I just find it fun. On occasion, particularly with a show as plot heavy as DS9 becomes, I enjoy an episode that's there more for fun than for serious drama.
Also, side note, it's the first episode of DS9 I remember actually seeing, or rather, the first half of an episode I actually saw, since I remember about the last half or so being what I first sat down to watch DS9 with. I was eight or so and I was VERY confused, since I'd seen preview clips from Season 2 and saw Kira as a good guy. I remember thinking it was a flashback.