I voted for Gnome Shell (without extensions it's awful, but with them it's a good DE), and LXDE.
I don't like Cinnamon. I also never used Gnome 2/MATE and KDE, because my first distro was Ubuntu 11.04 (10.10 were falling into console, and i had no Linux experience).
After i switched from Mint 12 to Ubuntu 12.04 beta (i broke my mint installation), i could not use Unity (but i used it from 11.04 release to December)
Original comment:
My first Mint version was Mint 12. Before that, i used Ubuntu. I tweaked gnome shell a bit (set default theme, disabled monitor and music player extensions, moved clock to center), and i liked it. I never used Mate/Gnome 2 (mostly due to my first distro was Ubuntu 11.04; 10.10 were falling into console). I used this system for a long time, since the mid of December.
Few weeks ago, i’ve looked at Cinnamon screenshots, and i didn’t liked it. Because Mint 13 use it by default, i decided that i will switch to Debian, or go back to Ubuntu.
Around that period, i found out that i got two 2gb swap partitions. I turned the largest one into ext4 file system, installed Debian (right from Mint), and started experimenting. After i installed X server, i were searching for an DE, that will fit into this small 2gb partition. I’ve stopped at LXDE. It’s good, fast, but not as great as my tweaked gnome shell.
Few days ago, i broke my video drivers (black screen, can’t even switch to tty). I didn’t had Mint disk, because i installed it from Flash. But i had Ubuntu 11.10 disk. I’ve installed it, and i could not use Unity. That’s right, i used it since 11.04 release to the mid of December, and i couldn’t use it again. So i purged Unity, installed gnome shell, temporarily added Mint repository, and installed MGSE.
I could install Debian, but the fonts don’t look good enough, and i didn’t seen so awful Russian fonts before (it’s my native language).
Then i updated to 12.04 beta. MGSE didn’t worked, so gnome shell feel lot worse and unusable (now i understand, why Linus hate it).
I’ve manually installed extensions from gnome extensions site. Now, gnome shell is usable. The bottom bar is different, and Alt-Tab is Gnome 3 style, but i like it this way (because i use Alt+~ too). I’ve also installed «Battery remaining time and percentage» extension, and it’s very useful.
tl;dr: I like gnome shell with MGSE extensions, but i don’t like Cinnamon. I also used LXDE, it’s good, but not as good as gnome shell with extensions.
I voted for Gnome Shell, and LXDE.