Example is that GTK3.18 support was removed the same day that Ubuntu released the GTK 3.22 based Ubuntu 18.04. Result - users of Ubuntu 16.04 based distros, many of which are supported for another 1 to 3 years, can't use the Theme without locating older versions.
The theme is a low contrast theme so it really depends on the screen brightness if you see borders or the text, some elements don't even have borders - this makes the theme barely usable for portable devices.
The font color in Arc and Arc-Darker is not black, but lightgray
after prolonged usage, it becomes apparent that this font color, combined with white backgrounds causes too much eye strain
The color combination has been carefully engineered exactly for the purpose of making people comfortable, while staring at the monitor for a prolonged period of time.
The design is extremely basic - using just 1 color accompanied by 3 shades of grey, OneStepBack manages to be a very functional theme without adding any flashy.
Besides this Gnome Shell theme there are multiple GTK and icon themes that match, giving the user a wide variety of themes to mix and match that still look great together.
Moka offers suers easy to follow instructions to download including PPA's for Ubuntu based distros and Fedora specific instructions to install its repo.
You can notice jumpy behavior when switching from a forefront window to window behind it. Both windows jump a little which can slightly disrupt normal working flow.