Dark Angel was one of the best shows ever (of course, this is coming from a devoted fan of sci-fi). One of the things I loved about it was the way they did season breaks. Other than shows like Charmed and Angel try to get the viewers to believe that there was no time lost over the summer, and the first season ending of Smallville put the summer break between the first two episodes of the second season, which was just wierd.
The Dark Angel writer were able to write in two to three month periods in which nothing vital happened, and make it believable. They understood that a good cliffhanger doesn't need a gun pointed at the hero's head or a "someone's dead--but who is it?" gimmick. The best cliffhangers happen only when you really care about the characters, the ones that make you wnat the characters to be okay, not just physically, but emotionally too.
Dark Angel was one of the first sci-fi shows I ever watched, and I credit it for nurturing that love of all things "out there" that I continue to cherish today.