I was using Fedora for a few years as my full-time operating system, and being a heavy Mac user and occasional Windows user, I came to really love GNOME 3. (I'm back on OS X after switching jobs.)

GNOME has a javascript extension library at http://extensions.gnome.org/ to easily tweak it to your preference. It's also easily themable using CSS, I was using the ARC theme (https://github.com/horst3180/arc-theme)