For me the only appeal is connecting in line with my work and interests rather than my circle of friends and friends of friends on Facebook. If the kind of people I follow (use that losely I guess because I only look at it occasionally miss a heap of Tweets) moved to a platform which allowed longer form conversation and better image/video/link support I would have no problem moving on.

As it stands the threaded, no character limit format on hacker news is far better for getting insights on topics I care about than Twitter.