I know what you mean. Springheel used this once in a tutorial for traps, but in the end I just copied his methods and didn't understand much.
However, there is a different S/R application I understood and I find very handy. If you pick a random frobable entity, go to S/R and click on responses, you can select the Stim "Frob".
If you then press the right mouse button in the response effects area, you can activate effects such as:
clear/add targets on AI
turn off/on lights
play sounds
remove items
run scripts
change frobability
set skin
trigger entities
set light color
Unfortunately, the last one (changing the light color) doesn't work so well. I have noticed that this effect is reset when you save and reload the game. However, I have not yet noticed this with the other effects (and frobability/remove works perfectly, I use them all the time.
But that's only one of the possibilities, certain stims, as I understand it, work on approximation, and you can do cool things with them.
There's also a Wiki entry written by Sparhawk, who coded it. Unfortunately I don't understand much there either.
I don't even dare to ask, because Geep has already done so much, if he could revise this section and provide understandable examples for both stims/responses.
@Geep Didn't you once open a topic in which you explained the use of stims? That was very informative, but unfortunately I can no longer find it.