Having tested WHS, I can say that anything you can do connecting to Samba you can do connecting to WHS. I had my wife's iMac and my Linux systems connecting just like they did to the Linksys NAS I used before. However, only the Windows boxes benefited from the backup system in place. Now that Windows is quickly becoming an endangered species at my house I see no real benefit for me in WHS and have switched to Linux on my file server.

There is an open-source equivalent in the works, though I'm not sure just how quickly it will reach a release state. It's called Ubuntu Home Server. It's supposed to be able to give the same benefits to Mac and Linux that WHS gives to Windows.