From the Writer Zone blog:
Thank you to everyone who tried out the beta releases of Writer over the last year and gave us feedback. Over 1.5 million of you downloaded our last beta release, and your input helped make Writer the product it is today.
Our goal from the start has been to help make blogging more powerful, intuitive, and fun for everyone. Today, we’re proud to announce that Windows Live Writer 2008 is now available!
As promised, it now works properly on 64bit systems:
We have heard from many of you about the pain and frustration in the last beta release when support for installing on x64 systems was not supported. We're happy to share that this has also been fixed and now installation on Windows Vista x64 is fully supported.
Link: Windows Live Writer Download