I've had the honor to play with Live Mesh and so far I'm very impressed.
Right now you only have the folder sharing scenario. Yet it was cool to have my Onenote notebooks synchronized across my tablet and workstation and share with other people.
For people that kept asking what the "Mesh Platform" can do, check out the below article to look at a simple yet powerful scenario.
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Having a task tracker application that runs on all my mesh devices and synchronize their state: simple yet wicked cool.
Come to PDC to learn more about the Mesh Platform, the SDK and make sure you do ask questions directly to the people who built this stuff. They'll all be at PDC!