Ubuntu One is a file synchronization service that allows you to share files among multiple computers. You place files into your Ubuntu One folder and they get synch'd with your account on the web. Files can also be shared with other Ubuntu One users as well and if you publish them they can be shared with anyone on the internet. It's similar to other synchronization/sharing services like Dropbox. 

If you've been using Ubuntu One with larger files and your internet connection speed is not the fastest, then you've probably noticed that it can take quite a while for larger files to synchronize to the server. When viewing your Ubuntu One folder in Nautilus, you're not given any information as to how much progress has been made on files that are currently synchronizing. Files that have completed synching show a green check mark while files that are currently synching have green and blue circular arrows.

There is a command line tool that can tell you the status of just about anything having to do with Ubuntu One. The command is called u1sdtool. That stands for Ubuntu One Synchronization Daemon Tool.

To see which files are currently being synch'd, use:

The output will look something like this:

operation='Upload' node_id='3ab2e6bf-4321-23c0-bad7-f6024234fe16' share_id=''
path='/home/linerd/Ubuntu One/really_big_file.avi'

To check the progress of the synchronization use:

The output should look something like:

Current uploads:
  path: /home/linerd/Ubuntu One/really_big_file.avi
    deflated size: 89374646
    bytes written: 30530448
Current downloads: 0

There are several other options available. You can look into them by viewing the man page for u1sdtool.