The app retains the polished and clean interface that came with Tweetbot 3, with its signature tweet streaming feature and customizable bottom tabs. There are also some new features, notably the support for Safari view controller, the reason being the links from tweets can now be viewed native in Safari with ad-blocking functionalities if you have one installed, and the pages also load that much faster because of Safaris nitro JavaScript engine.
The new 3D Touch features are fantastic additions - I particularly enjoy being able to peek into tweets and see replies, likes, RTs.
I also wanted to highlight how awesome the sync between the iOS app and Mac app is. I can literally read my timeline on the phone sitting on the toilet bowl and pick up where I left off at my desk on my Mac afterwards.