Well, I go away for awhile and a DS9 thread pops up. First, I agree with whoever was talking about that certain type of DS9 fan, I think they get that way to counteract all the "I hate DS9 but never really watched it" folks who I also really don't like, not that it makes those certain DS9 fans any less annoying. I grew up a trekkie, my mom had about 1/2 of TOS on tape so I watched those constantly growing up. When TNG came out, it was a family event to watch those, so naturally when I heard about DS9 I was thrilled! Watched it from beginning to end, missing only a couple episodes which I have seen now thanks to DVD and it is definitely my favorite. I watched Voyager too and really tried to watch Enterprise, but haven't really kept up with it.
My favorite episode, that is really hard, but I will have to say The Visitor which I don't think anyone has mentioned yet. I have never been so moved by an episode of Star Trek or any television show, moved to tears multiple times in the episode. It is too bad they didn't do more with Jake especially in season seven, the father/son Sisko stuff was always welcome. I was going to list other episodes that I really liked, but there are just too many
I really liked the character building in DS9, I always loved the small amount they did in TNG and TOS and it was what I always wanted more of in Trek. The exporation of many of the races, mostly Bajorans and Cardassians and later the Gamma Quadrant races. All the political intrigue was great. The fact that it explored a lot more of the darker side of things while still having time for fun times. I really appreciated how religion was always treated with respect, they really had a tough balancing act that I thought they pulled off. The Sisko/Prophets storyline always fascinated me. And the characters were great and had great stories. Sure, they series wasn't perfect and DS9 had a few really terrible episodes, but it always seemed like they were pushing the boundries on that show. Occasionally it was really bad, sometimes good, sometimes brilliant, but rarely was it ho-hum.