Our team has published a Channel 9 video listing the new features in Windows Live Mail Desktop beta. This is a great chance to get a tour of the features that are being released.
This video covers most of our current features. A few are not shown, such as Active Search (see blog post on that feature).
The WLDM Channel 9 video is available here: http://channel9.msdn.com/Showpost.aspx?postid=200389