So, I wanted to beta test the new Windows LIve Writer with this myitforum.com blog, and here are the settings you need to use:
Choose "Another weblog service" and click Next.
Be sure to replace "<username>" with your actual username in both locations. Click Next.
This one was tricky to figure out, but here are the settings as they should be. Click Next.
When done, you get this confirmation screen. Click Finish.