Twitter has introduced a new interface that promises to be faster and a more engage experience. The biggest change is the 2 pane interface. The left panel continues with the traditional stream and a right panel has all your "Followers" and who you are "Following" with Trending topics and Trends. This panel changes if you click on rich media from the original stream such as photos or videos. You no longer need to leave twitter.com to look at photos or videos. Twitter has signed with over 16 partners such as twitpic, yfrog, and youtube to name a few.
I really enjoy the fact that you do not have to leave the the website to view images and videos anymore. I also like the new pop up window when you "Reply" to a tweet. Twitter keeps you inside the site to experience all the content. Keep in mind that this is still a preview and that changes can still be made as user(s) like myself continue to experience the interface.
I think the biggest drawback of the new interface is your "Branding" if that is important to you. If you are just a regular user(s) it shouldn't be an issue but to the person who relies on "Brand Awareness" some tinkering maybe required for you. The bottom image showcases Kevin Frankish a morning tv show host in Toronto with his Twitter landing page. You can obviously see that certain areas are covered with the extended panel interface. I also did not like the "Auto Update" on the main stream because it has a slight delay to refresh. If you are viewing photos within the panel it does not showcase how many have viewed the photo which is an important metric for some. Overall, with anything new it will take time to learn and untrain the mind from getting use to the new interface. I'm sure Twitter will continue to tinker and also add more options as the new Twitter rolls out to everyone.