I'm in the progress of migrating my vBulletin 3.8.5 board over to XenForo. So far, the importer has been working great... but it's only grabbing 279 of my 12,000 attachments. It does not error out, but finishes and gives me a Imported 279 items. (1 minutes 5.84 seconds). The attachment directory is on the same server and I can verify that the attachments work with the old vBulletin instance too.