Canonical announced the file services for Ubuntu One has been discontinued. Your data is available for download until the end of July - if you haven't taken action already, you need to do so now in order to ensure you have a copy of all your data.
In order to make it easy for you to retrieve all of your content, Ubuntu has released a new feature that lets you download all your content at once. The website https://one.ubuntu.com/ has been updated with instructions on how to conveniently download all your files.
In addition, you still can use Mover.io's offer to transfer your data to another cloud provider for free. And the Ubuntu One web interface is available for you to download individual files.
The previously announced option of downloading your files as a zip file is producing unreliable results for a small number of users and therefore that option has been removed. If you already retrieved your files as a zip file, Ubuntu encourages you to check for the validity of the zip file contents. If there are problems with that file, please use one of the options above to retrieve a complete copy of your data.
Remember that you will have until 31st July 2014 to collect all of your content. After that date, all remaining content will be deleted.
The Ubuntu One team
NOTE: To remove the annoying "Ubuntu One is closing down soon" pop ups, you can remove Ubuntu one with the following terminal command (I used this and it worked fine):
sudo apt-get autoremove --purge python-ubuntuone-storageprotocol
Just make sure it doesnt try to remove "ubuntu-desktop" :) Alternatively, if you dont trust the command line, Go into the Software Center and search for "python-ubuntuone-storageprotocol" and uninstall that.