The mobile Twitter site had been a vastly more miserable experience compared to even the worstest apps, but now, it's a strikingly good web app, with full Twitter powers, all while actually looking clean and respectable.
It's currently most optimized for WebKit browsers—iPhone, Android, webOS and Symbian—but BlackBerrys work too. It's built entirely using Twitter's own APIs, hence the announcement post's title, "Takeout Dogfood." (Why not ice cream?) For now, you'll have to go to mobile.twitter.com to use it, but they'll eventually be transitioning m.twitter.com over to the new site as they work out all the kinks. And so far, it's pretty impressive, even if it does feel a tad slower than I'd like at the moment.