I going to do better than give you my opinion on DS9, I'll give you my opinion on all the Star Trek series. Please note, that I am not a Trekkie. I have never been to a convention, and do not own any seasons of any star trek show, I am however, a fan. I enjoy the series, without losing sensibility or reason.
The Original Star Trek show: It was ok, at best. Personally, I didn't like it, but it's from way before my time too. That may have an effect on my opinion. I found the story lines to often be unimaginitive, the acting to be horrible, and the aliens are just uninspired ripoffs of actual culture's and races.
The Next Generation: This is tied as my favorite Star Trek show. With the exception of the first few seasons, the show is generally well done, with original storylines, decent to great acting, and intrigiing characters. Most notably the character Data.
Deep Space Nine: I thought it was ok. I enjoyed most of the first few seasons episodes. The show's emphasis on religion and politics was an interesting change of pace from the typical "exploration" themed series. I thought it eventually grew stagnant, and lost interest in the show when it moved to it's "war" theme.
Voyager: This is the other favorite of mine. It took a brand new spin on the whole "exploration" concept. Again, the presence of an interesting character became a major draw for me. The holographic Doctor was an original character, and was featured in many episodes. Although I hate to admit it, Seven of Nine ( Jeri Ryan) also became a reason I liked the show.
Enterprise: While the actress playing the vulcan was enough to get me to watch the show a few times, the entire series was straight crap. Disjointed storylines, total abandon of all the previous series canon, and horrible acting destroyed the Star Trek universe for me.
Bonus: The New Star Trek Movie: Having not been a fan of the original series, this movie was easy for me to accept. It's "alternate universe" storyline fits within the established canon. While it lacks the typical Trek intelligence and falls short in some of it's acting skill, the movie was enjoyable for me.