While I have the Mesh bits installed for a few weeks I only recently started using it and was very handy when I wanted to get to some information on one of the Wiki's running at home.
I have some of the machines on my home network connected on the mesh now (see screen shot below) – they all are running Vista. It is quite useful and much easier to use than trying to RDP into various machines (assuming you can fwd the ports for various machines on the router). Another cool feature is I don't need to have any bits installed to access them (say from a corporate environment). You only need a browser to login to the mesh and get to the machines (I only tried this is IE 7 btw).
I have used a little bit of this so far and do find it quite useful; there are various elements of this that I have not really used yet (such as the sync. features).
I wonder if there will be an interesting convergence between this and WHS at some point in the future?