Woah! My head is spinning after watching this video demo of a Tweetdeck beta release which uses Twitter's new user stream API. It lets you watch people replying, retweeting or favoriting tweets in real time.
According to The Next Web, this functionality is available not only in the beta release of Tweetdeck, but also in that of Echofon. And if you're eager to see how crazy Twitter can be without needing to refresh anything, then "you can pay $20 for a registered version of Echofon for Mac, or sign up for one of Tweetdeck's preview releases." [TheNextWeb]