I don't think Amazon is going to try to sync with 3rd party software, but I wouldn't be surprised if the author of Calibre does implement something like that once the updates are released. He seems to be very proactive, with weekly updates. If that happens, though, I think I'm going to revisit my categories in Calibre before I use them on the Kindle. I wonder if we'll be able to have subcategories... ie categories Fiction, Nonfiction. Then under fiction, categories for fantasy, science fiction, mystery, suspense... and what about read and unread? Hm this could get complicated.