I have seen this theme, I installed it, but it still looks pretty different from the promises (look at the picture). As you can see my result (on the right) is pretty different from promised version (on the left). Does someone ever tried with a real success this themes and how? 
Several things are responsible for what we see on screen:
The "gtk" theme affects most of the window that you see in your program except for regions such as the title bar, the maximize/minimize/close buttons (to the left or right of the title bar), and the thickness and color of windows borders.
(I maybe stating the obvious here but you need to make sure that you're installing the GNOME theme that is appropriate to your GNOME version. Of late, there have been significant changes in the GUI of GNOME apps. The theme you linked to has been updated to accommodate GNOME 3.6.x.)
What you have installed is the gtk theme. So, only specific aspects of your program's window are affected. If you want the "whole appearance", you may have to download the relevant icon theme and possibly even a window manager theme. I'm afraid you'll have to do this on your own by contacting the gtk theme's developer and asking about the icon theme and the window border theme. The link you provided has some information on this.
