Linux Mint 13 is a Long Term Support or "LTS" release. This means that updates will be provided to users of Mint 13 and there will be no worrying about upgrading for several years.
Most distributions have several different desktop environments or "spins", but they only have one "official" release and as such that is the only one that gets long term support treatment. With Mint every desktop environment appears to be equally as "official" and so they all get the same support.

Mint 13 still has KDE and XFCE versions, but drops the GNOME version in favor of two new ones:

• MATE, a fork of GNOME 2. This version is almost exactly like Mint 11.
• Cinnamon, a fork of GNOME 3 that doesn't have any of the GNOME 3 desktop stuff. This version is almost like Mint 12.

These screenshots are of the Cinnamon edition. Click on the last section link at the bottom of the page to see the MATE version.

During boot Linux still finds it necessary to output command line stuff out over the boot splash. This looks ugly and should not be done.

One other thing that is worth noting is that the Cinnamon desktop requires 3D Acceleration to work. Since Virtualbox doesn't work properly anymore, and even VM Additions couldn't fix this mess, I had to create install media for this version of Mint and run it on my test machine.

The Cinnamon desktop doesn't look much different from the MATE one, except the bottom bar is now a different color.
From a Mint 12 user's perspective, the top bar is gone, and the GNOME 3 Shell full-screen crap that was present before is nowhere to be seen.

The menu is arranged like it was in Mint 12, it just has a different color to it.

MATE did the same thing, but the icons for Firefox and Nautilus are still rather mediocre.