I was really skeptical as well; in fact I've only had an account for 2 or 3 days now. Part of the appeal is similar to that of HN. For the most part, it's still mainly used by the early adopter, tech-savvy crowd. And, from what I've observed, the brevity of the messages actually seems to encourage dialogue: people are a lot more willing to to say something to you or read something you send them if they know it only involves a couple of sentences.