I'm using Twitter in this week and the API works "almost" perfectly while the website is down most of the time.
I've recently heard about identi.ca, so I decided to try it.
My first impression was bad, because I've seen many redirects of the page, and DNS changes sometimes.
But ok, I tried to register and again... I had problems. When I submitted the registration twice it just did nothing.
I then waited for a couple of hours then I've been registered to identi.ca.
Once I tuned all my account settings, the service has gone down. What happened? Too many twitterers have switched and now identi.ca is out of service? In the while Twitter has magically reopened its gate.