I know I might catch a lot of flak for this one.. I had been using ubuntu for quite some time and was quite fond of gnome 2 (and still am). When ubuntu switched over to Unity I was not a happy camper. After some break-in time and adjustment, I have actually found myself very much enjoying the Unity experience. I think it would go along well with the focus of PC-BSD in making it a very user friendly experience. I find gnome 3 to be very busy and un-intuitive, and KDE just doesnt "flow" to me. Gnome 2 /MATE is the only other option to me, with Xfce and LXDE as last resorts. I think Unity fits the bill quite nicely! Just my 2 cents!
Unity, GNOME3, GNOME2/Mate all first need to be fully and officially ported to FreeBSD before anyone can look down on those who choose to use them. Once they are FreeBSD ports, they can be added to PC-BSD.