OK, just watched the demo video and read some more.
The MetaWeblogAPI is not supported so I can't post from Marsedit, BlogJet, etc. Please support the MetaWeblogAPI and the MT extensions so that the hundreds of tools that work with these APIs work with MSN Spaces.
And although I thought I read that MSN Spaces supported blogging via IM, it doesn't. Pity! It would be cool for example to let the author of a blog, update via IM or to let the author's IM buddies post comments to the blog (somehow! not sure how to UI this).
Finally the very smart Dare Obsanjao (check out Dare's MSN Spaces blog) is working on the back end. I am sure Dare's involvement will result in it s*cking less much more quickly since Dare knows blogging, the MetaWeblogAPI, RSS, etc.