I've been using KDE theme called Baghira, which brings Mac OSX look and feel to KDE desktop, (http://baghira.sourceforge.net/) for long time now. I like to have this kind of cairo based theme engine in Gnome as well. This proposal to a Gnome theme engine developer... :-)
This was my KDE Baghira desktop before I start using Gnome: http://www.kde-look.org/content/show.php?content=30919
I was using KDE 3.4 at that time.