Light Themes evolved are modified versions of Ubuntu's default light themes, Ambiance and Radiance.
While there are no major UI changes, the "evolved" Ambiance and Radiance benefit a more 3D look giving an "on top" of the desktop feel, look strengthen by the modified shadows, too.
How do we install Light Themes Evolved 0.1.8.27?
Add the following PPA (Oneiric)
sudo add-apt-repository ppa:victored/light-themes-evolved
sudo apt-get update
sudo apt-get install light-themes
This new themes will replace the default Ambiance and Radiance.
To revert to the default Ambiance and Radiance:
sudo apt-get install ppa-purge
sudo ppa-purge ppa:victored/light-themes-evolved