Don't add the 3.0 repo and run it all yet. It's not ready for that. It's in testing.
I know that at least these three packages in the repo in their present state will break your system: uberstudent-xfce-default-settings, uberstudent-repo-configs, and docfetcher-installer. There's also an apport hook issue I'm trying to track to the offending package. Most of the packages are pretty much ready, though, except I need to go back and check their dependencies. I'm currently testing everything and working out all the issues; then, I'll build 3.0.
If you have a raring-based virtual machine or an installation of it on a harddrive section, and are game to help test things and don't mind things possibly breaking, please do use the repo and report back.
Here's how you can add it:
sudo add-apt-repository 'deb http://uberstudent.net/ plato main non-free contrib'
wget -O - http://uberstudent.net/uberstudent.gpg.key | sudo apt-key add -
Add only one package at a time if you decide to help with testing.