@Zach - thanks for the review.  Sorry that it has taken a few months to pick this issue back up.  Anyway, here is an updated patch.  It is pretty different than the previous patch, to the point that I would consider it a completely new patch.

Anyway, here's a basic rundown of what the patch contains:

Two functions in Modules/posixmodule.c were modified to handle bytes objects as well as str objects:  win_readlink and _getfinalpathname.  This was necessary to allow os.path.realpath() to continue returning bytes when supplied with bytes.  I know you said in your review that you didn't care about this because using bytes paths on Windows is deprecated, but I think it still important to maintain backwards compatibility.

A new implementation of realpath() was added to Lib\ntpath.py, used when _getfinalpathname is available (when _getfinalpathname is not available, realpath remains a synonym for abspath, as it was previously).  The logic here has been completely reworked and is roughly modeled on the realpath implementation from Lib\posixpath.py.

A number of tests were added to Lib\test\test_ntpath.py for realpath() functionality.  Three of the tests were based on realpath() tests from test_posixpath.py, but one is completely new:  test_realpath_broken_symlinks.

A note about improved Windows support was added to the documentation for realpath(), but no other doc changes have been made.

Anyway, feedback is welcome - I'd love to get this code in sufficient shape to see a working realpath() implementation for Windows land in Python.