Nexus 5 is an Android phone, so you must be using Ubuntu One Files (Android) application to sync files between your phone and Ubuntu One Web. Assuming that you do, I am enlisting some features of the Android app -
Ubuntu One Files (Android) application provides follwing features -
- Sync files from Ubuntu One Web to desktop and vice-versa
- Auto-upload images from Android to Ubuntu One Web when enabled.
- Selectively sync files / folders from desktop to Ubuntu One Web
- Download / Upload files or folders to and from Ubuntu One Files app on Android
However, it does not yet provide feature to -
- Auto-upload music files (*.mp4, *.mp3 etc.) or any other file types apart from pictures to Ubuntu One Web.
- Automatically sync updated file versions from Ubuntu One Files app to U1 Web or vice-versa.
In a nutshell, Ubuntu One Files app is still in a nascent stage as compared to Dropbox or Google+.
Be patient, and they will build it for you!