On Scientific (Scientific Linux 6), kde, gnome, lxde, xfce, icewm are all functional.  LXDE is rather minimal as no distribution for this OS exists but I was able to piece together enough of the required packages to get it minimally operational, the others are pretty much fully operational.  As with Zorin, KDE’s default configuration does not include a logout widget, so first thing you should do if you use it is add a logout widget to a panel.