Thanks to all for the feedbacks I received for AvalonDock. I had no much time during last 5 months to dedicate to AvalonDock. But now I'm going to post first release of AvalonDock. Of course this version will lack some features but I'm quite sure that in one month AvalonDock can reach CTP release. If you have any question post to this blog or append it to http://www.codeproject.com/KB/WPF/WPFdockinglib.aspx article.
I will publish an explaining article on CodeProject to illustrate AvalonDock features.
Here you can see some Avalon screenshot :