Twitter has been working so well lately, outages are actually notable again. The site is currently down as well as the API, meaning no Twitter client is working either.
Normally, when a big site goes down, people take to Twitter to vent but, well, they can't do that now and, while you may see a couple of people complaining on Google+ or even Facebook, it's just not the same.
Twitter has acknowledged the problem and is working on fixing it, though it hasn't provided any details on what's wrong.
"Some users may be experiencing an issue with our service. Our engineers are currently working on this issue," is all it said
It's a major outage, in that it seems to be affecting all users as well as the API, though some clients may work sporadically, but that doesn't necessarily mean it will take Twitter a long time to fix it.Update
: Still no details from Twitter, but the site is up and running, so is the API.