Thanks for the module, really like it.
There is a Live Writer Plugin that I wrote, to insert source code formatted for GeSHi Filter. I know a lot of people using WLW, so I thought you might find it useful to mention the plugin in the description of the module.
Details are here: http://www.etapiscium.net/blog/windows-live-writer-plugin-insert-geshi-b...
Plugin's here: http://plugins.live.com/writer/detail/geshi-server-blocks
Source is here: https://github.com/etapsc/WLWGeSHi