By utilising the new "OAuth" method of accessing the API of Twitter, tweets will appear faster in the updated app
The biggest update is the ability to view YouTube vidoes and Flickr images in TweetDeck preview windows. Till recently, the preview window was limited to viewing Facebook photos and previews of some links. This extended functionality means you never have to leave TweetDeck and open a browser.
Other updates include, the new "Column Navigator" which allows faster navigation through the multitude of user-defined columns, the ability to edit the definition of search columns and an enhanced help service including a "getting started" video. In addition there is the usual gamut of fixes and tweaks.