Hi,
in case there are some Gallery3 users around..
just a quick note to inform that I wrote a small Python script that can be used together with the Command-line sharing plugin to upload pictures to Gallery3.

More information and installation instructions can be found in this post to the Gallery3 forums.

EDIT: pylibgal3 has now been added to extras-devel. After installation you just have to edit the command line in Command-line Sharing plugin setup to something like this:
g3_share -i %s -o %s -s your.gallery.com -b /gallery3 -d "Test/Incoming Pics" -u g3_username -p g3_password