OK, I'll admit first off I don't know what I'm doing. I was able to install v5 trial in a test site and set up the default database for it. I had expected to be able to export my v4 database and import it into the v5 one. But field names are different in the new version, so I'm getting errors and import fails. I've even tried doing an export/import just on the Categories, to see if I understood it better, but even then there's a difference in field names - old says father and new says parent (#1054 - Unknown column 'cat_father_id' in 'field list' ).
Anyone care to enlighten me?