What are some alternatives?
When comparing Iris and Moka, you can also consider the following products
Materia - Materia is a development environment to build advanced mobile and web applications.
Zukitwo - Zukitwo is a Gnome Shell and GTK theme that currently works on Gnome Shell 3.14 and the latest version of GTK.
Eyeleo - EyeLeo is a handy PC application that reminds you to take a break for your eyes.
adapta-gtk-theme - An adaptive Gtk+ theme based on Material Design Guidelines - adapta-project/adapta-gtk-theme
Arc - Arc brings your favorite games, communities, media and
Elegance Colors - Elegance Colors is a customizable chameleon theme for Gnome Shell 3.6 - 3.14.