My strategy for roaming user profiles in a mixed NT 4 and Windows XP environment is not to use them. They aren't two-way.
Regarding User State Migration Tool, Microsoft is posting some killer documentation for this tool. It describes all the different commands use you can use in the INF files to customize it and corrects some errors in the original documentation. For now, take a look at the Step-by-Step Guide to Migrating Files and Settings paper. Keep an eye out for the new documentation soon.
This was first published in May 2002