I recently tried the new ubuntu one iphone application. You can sync all your contacts from your iphone to your ubuntu one account and vice versa. Its a very basic application and does not support your files or notes you have stored on the ubuntu one cloud.

Your have to sign up for a separate mobile account on the one web site at https://one.ubuntu.com/phones/ and then enter the username and password it generates for you into the app.

Looking forward to the next version!