Microsoft now provides a tool called robocopy that makes mirroring directories much easier. I found it from the deprecation warning in xcopy. Very useful and nice that it is included with the OS.
Robocopy - Wikipedia, the free encyclopedia
Very neat service from MS. It allows people to install the foldershare client on the machines which are to be synchronized. Then foldersync will manage getting your folders in sync automatically. The TOS are a little rough though. They basically say that MS is policing the space and has the right to review and remove your data. A bit strong. But a SIMPLE solution for people with multiple machines.
Technology-Escapades Â» Canâ??t live without it: FolderShare
Windows Live FolderShare beta