I use XeTeX on a daily basis, Jonathan ('tho XeTeXcharclass far less frequently) and would be happy to test your version on my production suites, but in order to do so I would require a Win64 (or Win32) build.
You can test the new experimental XeTeX on win32 by http://members2.jcom.home.ne.jp/wt1357ak/xetex-exp-w32.zip The file will be removed in due time. Best, Akira -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex