Cinnamon, the GNOME Shell fork used by default in Linux Mint 13 (Cinnamon Edition), has reached version 1.6, getting many new features: a new 2D session, workspace OSD, new applets and lots more!
In my test, the Cinnamon 2D session was very slow, even though my computer is pretty fast, so it seems this feature isn’t ready yet. And in fact, in the Cinnamon 1.6 release notes it’s mentioned that Cinnamon 2D is used to “troubleshoot compatibility problems with Cinnamon”, so it doesn’t look like it’s intended for everyday use just yet.
Also, Nemo, the Nautilus 3.4.2 fork has been integrated with Cinnamon, replacing Nautilus. This of course doesn’t mean you can’t use Nautilus or other file managers if you want to, but by default, Cinnamon will use Nemo (e.g. for drawing the desktop, etc.).