FlatStudio is a very nice, modern and flat GTK3 theme based on the colors from the MediterraneanNight theme by the same author.
How to install?
For detailed installation instructions please see the following tutorial created by Softpedia: http://news.softpedia.com/news/How-to-Install-GNOME-Themes-in-Ubuntu-11-10-231213.shtml
What's New in This Release: [ read full changelog ]
· The theme has been ported to Gnome 3.6
· The theme is fully integrated with Nautilus 3.6.x and Nemo (cinnamon 1.6.x)
· Known Issues: integration with nautilus 3.4.x (ubuntu 12.10) is not total but acceptable, will be fixed later
· Inside is also a version compatible with Gnome 3.4 (FlatStudio-G3.4.tar.gz)