I used twhirl for two years. Now I have to say it is not the best one any more. I googled it and find MetroTwit.
I feel the look of it is simple and clear. I like it. Users can custimize the layout. From two columns to three or four columns. It can conain my own timeline, mentions, favorites and etc. Skins or themes are changable. And also notification system included.
Firstly, Drawing inspiration from Microsoft’s Metro design language, MetroTwit celebrates an elegant and clean user interface that’s beautiful to look at and a pleasure to read. I use the larger text to shown the content. I put the window in full screen on my second monitor.
Secondly, Taking advantage of the latest Microsoft .NET 4.0 and Windows Presentation Foundation 4 frameworks, MetroTwit is a first-class native application that shines on Windows. Yes, I have to install .NET 4.0 before install it.