Nothing breaks news faster than Twitter. That is what I like about it best.
Or if I am watching an event on television I will have twitter on the iPad and then I follow what other people are saying about whatever I am watching. Be it sports or a Prez debate it really adds to the experience.
Other than that, I don't find it useful very often. I don't bother doing any kind of commercial stuff with my personal account. We do have a company account and only tweet once in a while because it does not suit our customers very well.