Picard works great with local filesystems. I've tried to use it through the remote server feature of gnome, and it could find files, help we update their tags, but I couldn't save the modifications.

Here's the error that was triggered when picard tried to save metadata:

Feb 11 19:38:01 rsertelon-desktop picard.desktop[24651]:     f = open(filename, 'rb+')
Feb 11 19:38:01 rsertelon-desktop picard.desktop[24651]: IOError: [Errno 95] Operation not supported: '/run/user/1000/gvfs/sftp:host=xxxxx,user=xxx/home/xxx/music/path_to_file.mp3'

I used picard this way because I store my music collection on my dedicated server with ampache for web access and subsonic app on my phone.