I was also very skeptical, but finally I found one good use for Twitter.

If there is some real-time trouble (e.g. you couldn't access your Gmail account, or Hacker News), Twitter is the first place where you can confirm your suspicions (and sometimes even find a solution/explanation).

On Twitter you can find out in minutes if there is anybody else having the same trouble as you, instead of hours till Google indexes blogs with complaints.

Searching Twitter is now my default reaction to figure out what's going on:

http://search.twitter.com/