I kinda go both ways with the summaries. As a reader, I like a general idea of what I'm getting into when I click on the story, but a short, intriguing summary works too. Sometimes it's fun to not have a clue and click on a story just to see what the summary even means. I don't like the super long summaries that tell half the story or the whole back story leading up to that point.
As a writer, I think most of my summaries are the shorter, vague kind because I don't like to give too much away. Sometimes, like with BMS, Undead, and 00Carter, I get longer with it.