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.
It's the only Twitter app I use on my iPhone and iPad. I like how smooth it it and the many useful feature sets it has. I also like the look & feel of the app, the sounds are not annoying, yet still grab my attention.