Linux already has numerous desktop environments, KDE, Gnome, LXDE, XFCE, and recently, Unity by Canonical. In addition, there is MATE a fork of Gnome 2, and Trinity a fork of KDE 3. These of course are only some of the more popular ones, there are tons of other lesser known ones.
So why has Gnome 3 been forked, and why does Cinnamon stand a chance? Well, first of all, while Gnome 3 brings many technical advantages, it also comes with a completely new way of using the desktop that not everyone will be comfortable with.
With the release of Linux Mint 12, the Linux Mint developers created extensions for Gnome 3 that brought back a lot of the Gnome 2-style UIs however, there is a limit to how far one can go with just extensions. So the Gnome 3 has been forked, with the intention of creating a new desktop similar to Gnome 2 but built on top of the technically superior Gnome 3.
Linux Mint, which is likely to feature this desktop, is the second most popular Linux desktop distro, after Ubuntu, which gives Cinnamon a fighting chance.
The project is now actively being developed on GitHub, according to the project's readme: "Cinnamon is a Linux desktop which provides advanced innovative features and a traditional user experience.
The desktop layout is similar to Gnome 2.
The underlying technology is forked from Gnome Shell.
The emphasis is put on making users feel at home and providing them with an easy to use and comfortable desktop experience."
You can find out more by visiting the project's website.