I mentioned Live Mesh in the TechNet newsletter a few weeks ago, and it seemed to go down a storm. Basically it means that you can easily share content between all of your devices so you aren't so tied to a certain machine for document or information. Overnight I received an email to confirm that it has not been opened up to the UK:
Expanded availability: If your country/region is the United States, United Kingdom, Australia, or New Zealand you can sign up for Live Mesh directly, with no waiting list, by visiting www.mesh.com.
N.B. Please remember that the product is still a technical preview (pre-beta)