Not trying to be a problem here, but what problem does this solve? Why does someone undertake to make a new desktop environment? Is XFce/Kde/gnome/cinammon/what-have-you not enough?
Mate is excellent and truly deserving of the title "modern Gnome2". It's my desktop of choice. Under the hood it's using a lot of Gnome3 tech while the user interface is familiar and usable for desktop users. The problem remains, however, that it is stuck with either a languishing GTK2 or at the mercy of Gnome with GTK3.
Perhaps you'd like to explain further?
The window list extension doesn't allow you to change the order of windows with drag and drop and I'm not sure if its possible at all. You also have limited options when you right click on them.
The workspace switcher as part of the window list extension or the stand alone extension are now text only menus that require multiple clicks to change desktop.
You cannot drag and drop launchers from the application menu anymore, in fact you can't have launchers on your panel at all anymore.
The system monitor applet is not visible on your panel anymore.
gnome-control-center is extremely limited, you must also learn to use gnome-tweak-tool and dconf-editor.
Also, classic mode just looks ugly and there is probably no way to change it without getting your hands really dirty.
Many of the things listed above used to work in classic mode but the functionality was removed in newer releases. There seems to be a trend of removing functionality from the desktop and moving it all to the activities overview.
But this is partnof their strength - one thing done well, and allowig the user to add everything else they want.
Problem 2: you want a VM with a DE but don't want to spend too much resources in it.
Problem 3: you have a modern computer but prefer to have a lightweight DE and let the rest of the resources be used by your applications.
Both LXDE and Razor-qt consumed about 100MB of RAM, I would expect something similar from LXQt. All the other DEs are heavier, XFCE is just a bit heavier but at least for me LXQt looks a lot nicer.
And as it was pointed out, it's a merger of LXDE and Razor-qt, so it's the complete opposite of the "many Gnomes" situation. Kudos to that.
I'll certainly build a VM with it to try it out, but my concern is that unless it gets some sort of traction it will just sort of fizzle out as folks graduate and move on to other jobs.
I've been using Mate (on Mint) happily, but I'll definitely give this a try on one of my laptops.
As for why the switch the Qt, I'm guessing it's because the next version of Unity/Ubuntu will be Qt based so this will be more compatible with that.
And Qt seems like is here to stay. So probably not bad decision from technical point of view too. It was nice when I used it.
LXDE on the other hand was specifically crafted for low-end systems. It's homepage says that it has been tested on PentiumII/266 with 192MB of RAM among others.
LXQt is the new merger of the two projects.
Personally, I'm glad to be done with overlapping windows and graphical file browsers. I use Xmonad, urxvt and bash.
If LXDE wouldn't exist, I would just use XFCE.