It's been a very busy time in Windows Live Mail Support and the product development team just launched the M6 version of Windows Live Mail. This is primarily a performance upgrade, so you should see better overall speed and response from Windows Live Mail.
For those of you using Mozilla Firefox, here is a list of features that you won't be able to see yet. We are still working on browser compatibility issues.
Resizable splitters between message list and reading pane
Drag and Drop
For more information about the update, check out the Windows Live Mail product team space