We do not officially support any of those even though inSync should work ok.
Paperpile uses the official Google Drive API. Within this cloud framework it's possible to put files into multiple folders and to have files with the same name. A client that tries to sync this to a local hard-disk needs to solve these two issues. The official clients do this well, inSync has trouble at least with the multiple folder issue.
The pull/push script Stephen posted does not care about any of these issues, actually there is a warning on the GitHub page:
Google Drive allows a directory to contain files/directories with the same name. Client doesn't handle these cases yet. We don't recommend you to use drive if you have such files/directories to avoid data loss.