To me, the people who are really into twitter all seem to be the same demographic, and that's usually bad news for a technology. It's those same people who used to like Usenet and the IRC that are now using twitter.
Twitter is something that intrudes on your life, and having it does not solve any problems, it adds stuff to what you already have.
But I won't protest too much, because it's possible I'm wrong on this one. I'll just wait and see. But frankly, I still don't see how I could somehow get my mum excited about twitter, even if it had all those features you spoke about.