I have installed ubuntu-one on a Lubuntu machine and indeed the file syncing works for all the folder that are shared.
My problem is that while on my ubuntu machine I can right click a folder and mark it as shared, I could not find a way to do the same under pcmanfm.
The only workaround I was able to find is to use the daemon via command-line:
u1sdtool --create-folder .
which works but is kind of clumsy.... any way to integrate in the GUI?