I don't use it, and don't think I will very soon though I have endless debates with my friends trying to convince me to jump on the wagon. At the end of the day I just find it too time consuming for the value I would get updating or following other's updates.

That being said I find it incredible that Evan and his team get very valuable insights onto the directions they might take twitter onto - take link 1 or link 2 as some of the recent examples I came across. That's I guess one of the most powerful outcomes of an ever increasingly noisy blogosphere environment.