As a blogger, the fact of the matter is, all I ever use Digg for is skimming to see if they have any cool videos to post. I don't even use Reddit for that anymore. I feel like their communities aren't super-welcoming like HN is, and have avoided them.
I think that Kevin realizes that to reach a broader audience the site needs to have value for people who don't choose to be active members of the community (or want their own little niches). Facebook does some of this, but it's too closed-off (unless you're on a fan page). Twitter does some of this, but it's too broad in some ways. If anything, it kinda takes the best elements from each.
Digg has a lot of problems with the way its audience has grown, and as a result, it's become overly-influenced by one core group of people: Young guys. Jezebel actually called them out on this recently:
http://jezebel.com/5531991/boys-will-be-boys-the-problem-wit...
If you want to win the influence game, you have to have more than just guys and more than just Justin Bieber fans. And the fact of the matter is, you can still have a huge audience on Twitter even without ever touching the trending topics. The current Digg, you have to roll the dice the right way. Reddit, you have to also keep your fingers crossed.
And to win the publishers over, you have to a) not treat them as if they're jerks for wanting to build traffic b) not waste their time. This design does both.
I'm going to use this once it goes up, because it doesn't feel like the deck is stacked against my little blog ( http://shortformblog.com/ for the curious).