The write-up for Version 1.1 in iTunes states confidently that “All files sent from other apps are accepted”. Perhaps this should add “…… but they may or may not be displayed”. pptx and xlsx files sent from GoodReader are “accepted” in the sense that they appear in the DTTG filelist, even showing the right filesize, but the type is shown as “unknown” and they generate a “Document cannot be displayed” message. iWork files (keynote and numbers) sent from GoodReader suffer the same fate.
Anyone trying this should note that synchronisation freezes if you attempt to sync with the files marked as Unknown still in the DTTG filelist. They need to be deleted first.