Clear is in a class of its own when it comes to both user interface (UI) and user experience (UX) in an iPhone app. It's simple, yet elegant as Jason Parker described it.
The no-frills approach to adding, deleting, and completing tasks with such a minimal UI can confuse some people at times, though. This short video walk-through will cover the basics, enough to get you started using Clear.
Once you get the hang of the gestures, moving around the app is intuitive. As I mentioned in the video, you can unlock up to three themes, each changing the color scheme of the app as a whole. You can find the secret to unlocking each theme in this post.
Clear is available in the App Store for $0.99 and is currently only compatible with iOS 5 and above.