I was curious about that service for a long time but I didn't manage to access it until today.
My first impression is that's impressive.
I added my corporate laptop and my home desktop and shared a folder and after a few seconds, I was able to see it on both devices as well as in the Live Desktop on the web !
Well I don't sync any corporate files for now as I'm always a bit paranoid but that looks really great ! You can find a description of the authorization and encryption mechanism used here : Behind Live Mesh: Authorization and encryption.
I also tested the Remote Control and it works fine... a bit slow but it works the display rendering is really impressive.
I'm now waiting to be able to add my mobile device...
Visit the Live Mesh blog for more information.