Editors' note, January 30, 2014: This review was updated to cover the features added in version 6.1.
The official Twitter app for iOS is great at the basics, but it might leave power users wanting more. That said, its reliable performance and slick design make it a good option to at least consider. Recent updates have added more features such as the ability to add photos to direct messages, the ability to reply directly with another photo, and new photo viewing features, but the app is still not on par with other third-party options.
Each time you boot up the Twitter app on your iPhone, it opens to the Home screen and lands on the last tweet that you read. Tap the Home tab to quickly jump to the top, or tap on any individual tweet to pop it out to a new screen. On this new screen, you get options to Reply, Retweet, Favorite, or Share, and in some cases you can view thumbnails images or other rich content contained in the tweet. What I don't like about this system is that you have to go back to return to your timeline from an expanded tweet. I would much prefer to see expanded tweets in-line (like you can on the Web site), without having to pop out to a new screen each time. Also, it would've been nice to get collapsible previews of links in-line as well.
The Notifications tab (formerly called Connect) charts your interactions with your Twitter friends, showing your mentions and letting you know when others retweet or begin following you. Next to that is Messages, where you can look directly at direct messages between you and other people without having to dig down to your profile. Finally, the Me tab lets you see stats such as how many tweets you've posted, how many people you follow, and how many followers you have. The Me page is also where you can see all of your previous tweets and swipe to scroll through a gallery of your previously posted photos.
When you're browsing your timeline, you can swipe to the left to view tweets from your favorite people, swipe left again to Discover new content based on what people you follow are interested in, and then one more swipe to see recent activity from all your connections.