Crucially, it is compatible with any blog tool, service or application that supports RSD (Really Simple Discoverability), Metaweblog API, or the Movable Type API. That includes Blogger, LiveJournal, TypePad, WordPress – in addition to Windows Live Spaces of course.
According to the Windows Live Writer Windows Live Space (yuk name… ie it’s blog):
Windows Live Writer is a desktop application that makes it easier to compose compelling blog posts using Windows Live Spaces or your current blog service.
The tool is consumer-orientated, offering a WYSIWYG interface very familiar to Microsoft Word. It’s also being touted as having particularly good photo publishing functionality – something which I know Sofia (my consumer user!) has been complaining about since she moved from Blogger to WordPress and so I know it’s a moot point.
We’ll have to see whether or not WLW actually achieves this claim – I’ll let you know once Sofia has used the tool in anger on her own blog. However WLW prefers to upload your photos by via newMediaObject API which is not supported by all blog apps. FTP is also supported, but I’m not sure how successful that is given issues around url locations etc.
WLW also offers direct importing of Windows Live Local maps and presumably other Windows Live tools in the future.