Hello Kovid,
Atleast two people,

, are interested in how you detect/keep track of what needs to be uploaded to a connected reader.
For example:
If I download some newsfeeds and have a look in the database then I can't find anything different from regular books that are in there. Still when i connect my reader those feedbooks will be uploaded and deleted, if that preference is set.
I had a look at the source but this is beyond my python skills to find out myself.
The reason I'm curious is that it would be nice to be able to add an epub of a newspaper through calibre-db.exe and have that automatically uploaded when the reader connects.
Could you explain or give a pointer to the relevant part of the calibre source.
Thanks,
Joop