The official Twitter for iOS app has just been updated to version 5.7 and brings with it some visual enhancements, particularly for the iPhone version. Most notably, tweet previews before you submit them and wider timelines throughout the entire app.
Twitter has been focusing a lot on user interface when it comes to the native app lately and that isn't a bad thing. The iPhone app got a bulk of the updates this time around featuring wider timelines and a preview in the tweet composer so you can see exactly what your tweet will look like before you send it. Other updates including the ability to receive notifications before sending a tweet.
You can grab the update now via the link below.