I just installed Ubuntu One on Windows and so far it seems that all I get access to are the Ubuntu files that have been synced when I use Ubuntu. This seems really pointless, since I can just get those files from one.ubuntu.com when I need them. When I tried telling the program that I wanted to sync one of my Windows folders (like My Documents, for example) it tells me that it isn't valid.
"Please choose a folder in your 'C:\SPB_Data' directory, and not overlapping with any existing folder."
(The directory SPB_Data is where the Ubuntu files get downloaded to from the cloud.)