"Muslix64" claims to have completely backed up an HD DVD movie and provides a Rapidshare link to downloading BackupHDDVD, a small Java-based utility that aids users to backup their HD DVDs. A YouTube link to see the program in action has also been posted.
The process isn't entirely fluid, and requires users to find their own encryption keys, meaning casual users will probably shy away from it. The similarities between HD DVD and Blu-ray DRM mean that if this crack actually functions the way it is supposed to, it may be a simple matter for it to be carried over. I'm very interested in finding out how founded these claims are.