I wasn’t sure if this would be possible, but I can now confirm that you can do a site collection backup on the Release Candidate build (14.0.4730.1010) of SharePoint and restore that it to the RTM (Release to Manufacture) build (14.0.4762.1000).
I used Central Admin to do the site collection backup (a new capability). Then I used the Restore-SPSite powershell command to restore the backup to the new server.
