Sun.misc.Unsafe usage in WindowsNativeDisppatcher

[Salter, Thomas A]

I was surprised that the implementation of WindowsFileAttributes.get uses Unsafe functions to directly access fields in the Windows structure returned by GetFileAttributesEx.  Does this give a large performance gain over a series of SetField calls in the C code?
-- If not, why add the maintenance issues of keeping Java code in sync with future Windows releases?
-- If so, why not do the same thing in the Unix implementation?