I've been using Mesh for a few weeks now and love it!
The feature that keeps coming to mind is the ability to share printers. I'd love to be able to share my home printer with another device on my Live Desktop. I'd hope to then be able to select that shared printer on the standard Print Dialog window.
This would allow, for example, my boss to print a diagram or image to my home computer on the days I'm working from home as opposed to having to send the actual file over.
But does that mean your boss's PC is on your Mesh? Or is he using your PC at work, which is (would be) sharing your printer at home?
Actually, being able to have a mesh of peripheral devices, which would be independent of the machine, would be a cool feature. Where the device is accessible by a "fixed" address and a password or from an account (like a Live ID) to which you've granted access.