Finally got a chance to test with Dropbox, Google Drive, and SkyDrive. All seemed to work very well. Uses an authentication system via your browser rather than just entering the username and password.
Works really well with one caveat: after uploading something, you have to refresh the folder set before you can delete the file (say if you uploaded something by accident).Security note
Inside the config file, you can see how many characters the password hash takes up:
Google Drive: 120
SkyDrive: 972 (!)
At least on the hashing alone, SkyDrive appears to have fairly high security. That said, although it doesn't store usernames or passwords in plaintext, and even supports a master password, I'd still put this program inside an encrypted volume like TrueCrypt.Screenshot:
Will definitely add it to the database sometime soon. Really terrific program to unify all the different cloud storage services.