It may not be the glossiest Twitter app for iPhone and iPod Touch, but it is among the fastest and easiest to use. You'll be able to post and refresh the screen from each of the four tabs. Your friends' timeline is the logical default, followed by replies, direct messages, and a search screen that can also show you public tweets from people nearby.
Composing messages is especially cool. After pressing the word balloon, you can begin tapping the keyboard or can press one of three buttons to geotag your tweet, take or upload a photo, and select a Twitter butty to reply to. This last auto-fill feature is a fantastic time saver.