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.
Ranked in these QuestionsQuestion Ranking
Pro Works great on old machines
Because it's older codebase is based on Gnome 2 which was the champion for desktop environments for a long time, it's very stable and has plenty of features which work perfectly for old machines.
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 Very stable
Code base is very stable and virtually bug-free.
Pro Decently customizable
Can customize a lot of its aspects, and using a window manager like Compiz.
Pro Distraction-free environment
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.
Con No official forum
Instead of having an official forum, users are redirected to their distributions support forums.
Con Not very likely to have new features
Since it's basically a fork of Gnome 2, and it's created to satisfy Gnome 'purists' it's very unlikely for it to add new features more in line with modern DEs.