Matt,
I am trying to get the filename in my Infopath form for a file that is contained in a SharePoint "Document Library", and not a form library. I do see the "Title" as you described, but unfortunatley, SharePoint is not putting the filename in the "Title" field.
SharePoint is using the "Name" property to store the filename in a document library. This field, "Name" does not show up in the Infopath Dataconnection.