The last time I switched my usual GUI:

Another vote for XFCE, and I'm glad to see how it's moving ahead. 4.8 just came out and added some nice improvements (the biggest for me is that now it's much easier to manage multiple monitors), but it still didn't need any major, revolutionary changes. Same old panel, same old window manager (which works beautifully, I might add), same old desktop. Nothing that needs to be changed. Does exactly what a DE should in my opinion - it allows me to get my work done, and stays out of the way otherwise -- the perfect balance of simplicity, customizability, and user-friendliness.

In fact, around my university there are quite a few kiosks for web browsing, and they all run Xfce on Fedora. That should say one thing: it gets the job done.