Seeing that there's a new test release of GhostBSD 3.0, a distribution based upon FreeBSD with GNOME, I was curious to see if they plunged into GNOME 3.x for their desktop environment. However, it turns out they haven't. GhostBSD 3.0 is just featuring a new GUI installer and will be shipping with GNOME2 as well as LXDE with the Openbox window manager.
As far as GNOME3 goes for FreeBSD/GhostBSD, this page simply mentions, "Gnome 3 is not ready yet. We will release it for tests and debugging to help FreeBSD Gnome Team."
In terms of GNOME Shell running on FreeBSD, when looking it up on Google and various forums, it seems to be mostly a troubled wreck right now. The GNOME Shell is in ports at x11/gnome-shell for those who dare.