There's a length MSDN article about this:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms740621%28v=vs.85%29.aspx

Executive summary: it's a can of worms.

However, let me point out the following sentence:
“Ports without SO_EXCLUSIVEADDRUSE set may be reused as soon as the socket on which bind was previously called is closed.”

...which seems to suggest we shouldn't use SO_REUSEADDR under Windows, since Windows sockets appear to have the Unix SO_REUSEADDR semantics by default.