MATE is a fork of the Gnome 2 code base, created in response to the many breaking changes in Gnome 3, many of which were met with disapproval by long-time Gnome users.
Pro Traditional desktop experience
The goal of MATE is to maintain the look and feel of Gnome 2, while maintaining compatibility with Gnome 3. To that end, it has also forked and renamed many of Gnome's core applications. It benefits from the years of work and polish that have gone into Gnome project, and has already been adopted as one of the default environments for Linux Mint.
Pro Multiple panels work great across multiple displays
This is very simple, but it is something much appreciate: the panel's window list is per display. So if you move a window over your second display, it gets transferred to the window list on the second display's panel. Multiple display support works very intuitively, right out of the box, with minimal tweaking.
Pro MATE is a serviceable choice
MATE is a solid serviceable choice for a DE. It is reliable and easy to customize. However, it lacks the panel management and rich choices of panel applets found in Xfce, and it lacks the icon placement in multiple monitors found in Cinnamon, KDE, or Windows.
Con MATE lacks customized desktop icon placement on multiple monitors
MATE does not permit placement of desktop icons on the monitor of choice in a multiple monitor setup. For example, with 2 or 3 monitors, with MATE you cannot place the desktop icons on the right-hand monitor -- they always move to the left-hand monitor. By contrast, you have control of desktop icon placement on multiple monitors with Cinnamon, KDE, and Windows.