Twitter has updated the web-based and Chrome versions of TweetDeck with a brand new user interface. The re-design includes a repositioned sidebar, which is now on the left. This sidebar allows you to access all of the columns in TweetDeck and an easy way to view lists and settings. The sidebar was previously located at the top of the app.
The update also brings a new flat icon to TweetDeck, and a slight UI change that shows a blue indicator at the top of a column if there are new tweets.
The company has yet to bring the updates to its desktop apps, but we should see that in the next few weeks.