Your timeline (you + those you follow)
Updating your Twitter status
Reply directly to tweets from MobileTwitter
Open Tweets in MobileSafari (handy for clicking on links..)
Direct message authors of tweets
Offline storage of recent tweets
Better chinese character support..
Bug fixes for tweets that don’t fit in their box..
Landscape mode for Update view
The only thing I don’t like about this app is that the keyboard is slid up just a bit and when I go to hit the spacebar I hit the different options at the bottom. My favorite feature is that I can open Tweets in Safari so I can click on links that are posted. This is available through the NPike.net source.