What can I do with Twitter?

I've come across a slew of articles expounding the advantages of using Twitter– for business, for blogging or for a host of other purposes.

I'm as entertained by reading and writing tweets as the next person but I'm not sure if I need yet another place to check for updates, posts and comments. I already read my work email, home email, Flickrmail, Facebook, IM and a handful of other community sites on a daily basis. Does Twitter replace or streamline any of this or negate one or more of the other sources?

Some articles for consideration:
Thinking about twitter feeding facebook status
Michael Surtees consider who say what to whom and where in the great debate, "Do I post this to Twitter or my Facebook status or both?"
Getting Things Done with Twitter
Use Twitter for financial, reminder, scheduling, health and more. It may be more useful than I thought.
Tweet Your Blog
Consider using Twitter to boost hits on your blog or website. Not a revolutionary concept but worthy of some consideration.
Tumblr lets users call in, queue posts, integrate Twitter
Ars Technica peruses the new additions to Tumblr, the already-abbreviated blogging tool.