UPDATE: released this as open source at http://code.google.com/p/wittytwitter/
I had some free time recently and decided to improve my original WPF Twitter client. This time, I wanted to focus on the UI perspective instead of the backend. With that in mind, I re-skinned it as Witty. Check it out and tell me what you think. It's still definitely a work in progress, but should provide the basics for interacting with Twitter.