From what I've seen of Twitter it looks pretty lame. Nothing about it very different from Facebook and some of the others.
Myspace is still my headquarters.
I guess it all depends what you want to get out of it.
It seems to work nicely for little quick updates....
On those two other sites, you'd probably post the full story while on Twitter it would have to be a very short thing followed by a link to the full thing....
So it's like a blog for people with short attention spans.
/jarmo