Some customers have decided to go back to hosting their own CRM servers to allow for better backoffice integration and troubleshooting. When receiving the CRM Online 4.0 DB from Micrsoft make sure you identity which version of SQL server you have. Also, make sure your new CRM server is at CRM rollup 20.
You will want to update the systemuserbase and remove the “windowsliveid” data from all users. This will cause issues with mapping and turning on older disabled users.
Additionally, you might have to create a temporary domain user without CRM access, then add that user ID to the record in CRM first, save, then update again with the new domain\AD account associated with that user. In most cases, the users will have existing AD accounts that can be used to map over the records.