James-
I would like to see each wikipedia be able to view what's in the Wiki-Commons from within their own wiki, but in their own language, and when they upload a picture, they upload to the commons, not the wiki, thereby saving server space. So, if I log into the German wiki, I can edit a description of the picture, and from English, Dutch, etc., I can do the same thing, and it all describes the same picture, not multiple copies of the same picture.
If you have a Commons image like
[[Image:Magnolia blossom.jpg]]
and you use it on a Wikipedia, e.g.:
http://de.wikipedia.org/wiki/Bild:Magnolia_blossom.jpg
then you can edit the image description page and add a German text. The image still comes from the commons - no disk space wasted.
However, it is not currently possible to upload files from any other Wikimedia project directly to the Commons. That's because to do so, the Commons would have to know who you are - and every wiki has its own account database. We could use something like "Eloquence@enwikipedia" as the identity, or offer an option to store the Commons password in the preferences, but I'd rather wait until we have true single login instead of using a temporary hack.
Regards,
Erik