I used Mate after the Gnome2 extintion, and I finished using XFCE as I think a lot of people will choose in this Gnome transition.
I proved all the Windows managers even the alpha ones as Pantheon.
I liked a lot E17's EDJ theme archive system.
You can package all the destop config in one archive, and you can save your own settings in one of this EDJ archives.
As well you can download and store them in order to switch it as you wish.
A similar way of doing it for XFCE with a site where you can upload / download themes would be great.