When I woke up this morning, I was surprised to see the new UI when I logged in to twitter.
The right pane is moved to the left while the below picture shows what expanding a tweet does:
Another major change is the what clicking on a tweep's name does. Earlier, such clicks used to open tweep's profile in the right pane. Now, it opens the profile a bit like pop up but only in a new layer on top of the window like this:
and this how the full profile page looks like:
Below screenshot shows a new stream, named 'Discover'. Discover is a dynamic information stream and the content is based on your location, your interests, what you follow and what's happening in the world. The more you use twitter, the better it gets
To end it, here's a short video that demos the new twitter interface: