Sorry to bump an old thread, but I am using Calibre as my library software with the 1150. I am still creating IMP's "offline" but that doesn't bother me especialy since if the original is a PDF it will take multiple steps to make it readable anyway.
The Save to disk option in Calibre works. I am lucky I have a card reader that supports the smartmedia format though. As a backup (or if too lazy to crawl on the floor to the card reader) I use impserve.
I haven't tried pointing impserve at the calibre directory yet to see if it will handle the multiple directories and formats though. Hrmmm... Nick?