(In reply to Ilia Mirkin from comment #1)
> Perhaps it's obvious to everyone but me... what's wrong in that screenshot?
> The dithering on the background?

It has major artifacts when moving windows and text that hasn't been refreshed
in a bit gets increasingly blurred out to the point it is unreadable. A
description of the problem can be found here: 
http://unix.stackexchange.com/questions/248223/antergos-ati-driver-issues
"no window effects that I could see. I checked in system settings and realized
it was running with Xrender instead of OpenGL, but when I tried to change it I
started getting weird artifacts, supersaturation, and odd glitches. Almost all
fonts became impossible to read."

and what has lead my here is documented on pages 115 and 116 here:
https://bbs.archlinux.org/viewtopic.php?id=79509&p=115