Delicious is less social and has a different focus, so no, they don't do the same thing.
We thought about building the service directly around Twitter and Facebook like you suggested. We could integrate them so that whenever you post on Howl, it posts to your Twitter/FB through the API. You're right about how its better than twitter, after all, who wants a stinkin shortened bitly link and a description? Give em big images and embedded video! Thanks.