Tweetbot for iPhone and iPod touch, Tweetbot for iPad, and Tweetbot for Mac have all been updated to support the new Twitter 1.1 API, and closer comply with Twitter's new interface display guidelines. In other words, to better conform with Twitter's branding and conformity policies. Changes include all avatars moving to the left (previously your avatar was on the right to help your posts stand out), and the way your @username is displayed.
Tweetbot, Tapbots' powerful, engaging Twitter apps for iPhone and iPad are on sale today only for $0.99. Tweetbot rarely goes on sale, and when it does, it's not for long. So, if for some reason you use Twitter and you haven't bought Tweetbot for iPhone or iPad yet, grab it now.