Ubuntu Studio is a derivative of Ubuntu intended for people creative in audio, video and graphics. The developers who bring it together have decided to deviate further from Ubuntu by using XFCE4 rather than going with GNOME 3 or Unity. They are happy with GNOME as it was and prefer to avoid the distraction of a radical change in user-interface. Because GNU/Linux is modular and flexible they can do this. More power to them.
This seems a reasonable approach to me. XFCE4 has a lot of differences from GNOME but it is pretty simple. It also has the benefits of being well-supported and mature. This is a more sure option than hoping for a fork of GNOME 2. It will be interesting to see whether Ubuntu makes this change increasingly difficult or whether a shift to the mother-ship, Debian GNU/Linux, would be in order.