Since announcing that we've started the beta of our implementation of the MetaWeblog API for MSN Spaces, I've received a bunch of positive responses from a couple of blogging tool developers. So far it looks like there'll be at least six blogging tools users will be able to use to manage the blog on their space after we launch the API.
Add at least one more - PostXING v2 will work with MSN Spaces via the MetaWeblog API. I don't think that it will work well with previous versions because I had to change some code in xml-rpc.net to handle the BOM as I noted earlier. If the xml-rpc.net library was updated for v1, I'm sure it would work there as well.