The first major feature of Cinnamon 1.2 are new desktop effects. "Cinnamon 1.2 is a first step towards reintroducing desktop effects and the ability for the user to define fancy animations or to turn effects OFF altogether." This includes introducing animation plug-ins for fading and scaling and 30 different transition styles. From the Cinnamon Settings area are also various ways to customize the desktop effects. Cinnamon 1.2 also has its own window manager now to replace Mutter of GNOME3. The new window manager is called Muffin and is a fork of GNOME's Mutter, which itself is derived from the GNOME2 Metacity.
Cinnamon 1.2 also has better support for desktop layouts by having just one panel at the bottom of the screen, one panel at the top of the screen, or panels at both the top and bottom of the screen (the classic GNOME2 layout).
If the layouts and effects of Cinnamon 1.2 aren't enough, this release is also easier to customize via a new Cinnamon Settings configuration tool. There's also new Cinnamon applets for accessibility, recent documents, removable drives, trash, and display (RandR-based monitor control).
Making things even better, Cinnamon 1.2 has its main menu "significantly improved" for searching and other interaction improvements. This release does also bring many bug-fixes (around 130 known issues addressed), but one of the limitations of Cinnamon is that it's now no longer compatible with GNOME Shell themes.
Read more about Cinnamon 1.2 on the LinuxMint sub-project blog page.