Cinnamon 2.0 has been only launched for a few days now and a lot of people have installed it on their Ubuntu 13.10 (Saucy Salamander) machines. That might have been a terrible mistake.
Installing Cinnamon 2.0 in Ubuntu 13.10 (Saucy Salamander) is a breeze, as it can be easily seen from our handy tutorial. Unfortunately, it also comes at a price.
Users have started complaining about the fact that Cinnamon 2.0 has somehow corrupted their Unity desktop environment. We ran a couple of tests on three different machines and all of them are now refusing to boot into the normal desktop of the distribution, Unity.
The reason might be a common GNOME package that is used by both desktop environments and none of the regular solutions worked, including the re-installation of Unity.
We recommend that, for now, you either install the new Cinnamon in Linux Mint or get prepared to only run Cinnamon on your Ubuntu.