I usually use Google Drive instead of Dropbox and similar ones to keep my files in sync amongst several machines, but I know drive does not work well with calibre due to the book ID (which drive reads as a duplicate mark - anyway google drive is #crapware, now I cannot trash it for I have many work documents into that, but I would not suggest anyone to start using it, right now). Anyway, this way I should install another sync-client and that's not a think I like the most.
What's more, I wonder what would happen if I kept 2 istances of Calibre open in 2 different machines (I can forget to shut one down, for example): is the sync not going to get messed up? What files does sugarsync (or dropbox, whatever) exactly sync? Just the books of even the database? If I am not wrong, the calibre library is made of several directory with book and a special file which is a SQlite database, what happens when there are 2 conflicting version of the database?
I am not sure I would like syncing calibre with a sync client, it sound much like a workaround, I guess a sync server would be much better.
tiziano solignani, da Mac