If you didn't know already, Tweetdeck was bought by Twitter a few months back. The London based Tweetdeck was the second most popular way people accessed Twitter, whether it were on the desktop or mobile apps. Twitter saw this so instead of going up against Tweetdeck, they bought them.
However since the purchase there has not been much development, until now. Twitter has just influenced Tweetdeck's desktop application which looks to be built from ground up. A lot of features have been removed, like adding other social networks such as Foursquare, however access to Facebook is still available. This one is being called version 1.0 and Tweetdeck's logo has also been changed adding a blue hue instead of the yellow.
It's become very minimal and live real-time streaming is still there which I thought was the best feature of the desktop application. Also columns are still available so you can keep up with multiple parts of Twitter at once, also one of the best features of the app. As you can see, I have my regular timeline, then my mentions, tweets by me and finally a search column on links from Twitter going to my site. You can add more columns however these 4 are enough for me. The more desktop real-estate you have the more you can fit on your screen.
The web version, desktop application and chrome app have all been updated with the new look. The mobile apps have been left in the dark however, there have been no updates or anything for them for months. This maybe because the Tweetdeck developers are now working on the official Twitter app.
Also the new version of Twitter was released yesterday, here is how to get it - How To Get New Twitter Layout for Web, Android & iOS