Recently I finished rewatching DS9. I remembered it being good but did not remembering it being that good. In fact I would go as far as declaring it as the best of all the Star Trek franchises.
Perticular highlights of the show for me are, the dominant war, evil Ricker, the Defiant, Bashir and Miles, and the Ferengi. I also really like the singing as well, with Vic in the hollow suite and Worf with his love of Klingon Opera.
I admit the DS9 is much harder viewing than TOS and TNG. But, it is the greyness of the characters and the complexities of the relationships which make the show so compelling to watch.
If it was possible to change one thing about then I must admit that I had kind of hoped that the Enterprise with Picard turned up as part of the final fleet!
So if you have never watched any Star Trek and someone is nagging you to watch it, go for DS9 first.