I’ve fixed one of the biggest holes in functionality in Windows Live Writer. It’s simple, but essential: the ability to count words (and characters and paragraphs) in your posts before publishing.
Windows Live Writer doesn’t really offer a way to extend the menu system itself, but you can create an “Insert…” plugin that just analyzes content instead of creates it, so it works pretty well.
Go get it from Windows Live Gallery. Let me know what you think!