I've been trying out Live Mesh in the last few days, and I am amazed at how well it works, and at the possibilities it opens in terms of the paradigm we use to interact with our resources. It's admittedly not a completely new idea, but it's new in the way it is realized.
Before I start: in the last few months I'd been using Mozy to do online backups to my personal laptop. Mozy installs a client tool that monitors changes in my files, and uploads them to a online repository. Another interesting feature is that it adds a new option in my windows explorer's contextual menu, which allows me to browse and restore previous versions of each file.
Live Mesh, in many ways, is similar to this. I browse my file system, select folders to sync to my online Live Desktop, and the client tool it includes uploads those files to the Mesh, maintaining them synchronized. I can then open them either from the web page or any PC with the client tool installed. I can also start a remote desktop connection to any computer in my Mesh. My desktop, anywhere. (but that would be an old slogan :-)).
Anyway, this is a very interesting development (still needing perfecting...), and I'm looking forward to use it widely, since it's still a Technical Preview).
If you want to learn more, while this is not yet completely public, the best source is the team's blog at http://blogs.msdn.com/livemesh/ .
Now, what I would really like to see in this platform is a Silverlight interface, using Deep Zoom to browse the "desktop". That would be cool, and an interesting desktop interaction model to try out.
This development is apparently in no way related to BizTalk Services, which kind of surprises me, and I have yet no idea what the programmability possibilities are/will be.