Maybe I just didn't RTFM, but I didn't realize until tonight that there is a great way to facilitate the setting of the non-primary sliders and buttons. Just hit the PAUSE button, and all the other controls become instantly responsive and the results are immediately shown.
What a boon, to not have to dork around trying to deal with a system that takes its own sweet time responding to mouse events. Just slide the sliders and immediately observe the results - very interactive!
Oh, very very minor point, just found a tiny GUI bug - when paused, if change a primary control causing system to unpause...the label of the pause button does not get changed back. Fixed in my version 2.40.01.07.