Here's my thought on the matter... The "Killer feature" here is the lack of killer features. There are no buddy lists, stupid picture icons, special groups, or karma-whoring incentives. It's just a simple place to exchange news that is generally relevant to a hacker community.

The lack of needless bells and whistles to constantly hold peoples attention will generally make this site un-fun for the unwashed masses of Digg and Reddit refugees.

BTW, welcome to hacker news...