Equinox is a new GTK2 engine already used by themes such as Elementary. The relatively new GTK2 engine has been recently added to the Ubuntu 10.10 Maverick Meerkat official repositories and has it's own Ubuntu PPA which, besides the Equinox GTK engine also holds a few great themes (click for screenshots).
Yesterday, a new version of the Equinox GTK2 engine has been released - 1.30, and with it, 2 new themes called "Equinox Evolution" and "Equinox Evolution Light" (they are complete with GTK and Metacity themes) are available in the PPA:
The differences between the two themes - as you can see, is the dark/light panel as well as the Metacity theme - rounded or squared. The first thing that will strike you when using either of these themes is the look of Nautilus (Elementary) which looks a lot like the Mac file manager and of course, the buttons which look amazing using the Equinox engine.
To use any of the Equinox themes, you must firstly add the PPA and install the Equinox GTK2 engine:
sudo add-apt-repository ppa:tiheum/equinox && sudo apt-get update sudo apt-get install gtk2-engines-equinox
The PPA also comes with everyone's favourite icon theme: Faenza so you'll also stay up to date with this amazing icon theme by adding the above ppa!
To install all the Equinox themes and the Faenza icon theme, use the following command:
sudo apt-get install equinox-theme equinox-ubuntu-theme faenza-icon-theme