I resonate with the desire for something in between Twitter and blog posts. Facebook has been filling that role for me so far, but not everyone is on Facebook.
I want to be able to publish thoughts at any scale, letting them evolve into whatever length makes the most sense. I don't want to have to think about what the appropriate size should be (fitting it into an existing structure).
It would be nice if the card textbox acted like the Twitter text box, monitoring the number of characters, at least when it's within range of tweet size (say, within 160 characters).
E.g., "Do I want to make this a tweet? Yeah, it's pretty close, so yeah, I'll just edit it down a few characters."
There are three main categories of existing content structures that I'm interested in so far:
I think of these as separate communities. With ThoughtStreams being yet another (and affording new content structures).
Right now, my tweets are auto-posted to Facebook, which I like. So Twitter integration will automatically give me Facebook integration too, at least for the tweet-size thoughts.
Eventually ThoughtStreams may work well for blog posts, but I'm guessing that I'll continue to author those directly in Wordpress (but perhaps announce them over in ThoughtStreams, and effectively Twitter/Facebook/G+).