No amount of training, or even hands-on practice, will create the competence that users had on the legacy system that they had used for years or even decades.  It is critically important that after go-live, users are supported proactively.  Proactive support, not just responding to issues but asking for feedback or questions, having office hours, coordinating Q&A sessions, listening to feedback – not only creates an mechanism to resolve issues, it builds the right kind of relatedness.