Gnome has the great advantage of being a Chameleon with its Theme options. Making your Gnome based distro looking like a Mac OSX is very easy:

• Download Mac4Lin;
• Click on the file Mac4Lin_Install_v1.0_RC.sh for an automatic installation;
• Install AWN and setup it up with the applets you need.

Since I installed AWN, I removed the bottom panel of my desktop.

Final result?