UbuntuOne is my cloud sync service of choice. Why? It's ready to serve, by default, on all Ubuntu desktops (starting with 11.04) and does an outstanding job of not only syncing the files in my user UbuntuOne folder, but music purchased from the UbuntuOne Music Store as well as other folders configured in the UbuntuOne Control Center. Each account comes with 5GB free. You can purchase 20GB more storage (plus Streaming Music Service for your mobile) for $3.99 per month.
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