There is so much that can be done with this game. When I go into the setup menu & see the goodies that can be toggled, it gives me goosebumps. I'll see if it's cool w/ Brad for me to go into more detail about that stuff, but let me say that there are things that ST will do, out of the box, that UT needs mutators to do. And they are all as easy to set up as toggling menu items. Skulltag is a Doom player's wet dream, but this is no dream.
Mellow also talks about csDoom a little as well.