tweetbot

If you like seeing replies to someone else's posts, the conversation view is generally superior and you have a Mentions tab in their profile. Searching keywords gives more results. TweetMarker/iCloud is huge and you'll appreciate it right away if you use even two devices regularly (Mac app will soon hit the App Store). And while I know it's not universal they do have an iPad app that's tablet-optimized, something Twitter regressed on in their last update.

Hope that helps. It's worth it and the one app I miss most on Android.

 

Tweetbot so far has been wonderful. It was a few bucks IIRC, nothing considering how often I use it.

 

It's good enough that I bought it for Twitter, then purchased it for App.net (NetBot) since Twitter is no longer giving me reasons to stay.