Re pre-heat etc, while I know a lot of dimmers have very good dimmer laws and things, most theatres do not contain these and when I am incoming to these venues I cannot really rip out their green gingers or STMs and shove some Chillis in instead, nice as that would be. If I am touring a show then I often want to be able to adjust pre-heat levels and dimmer laws so that the show looks the same without massive re-plotting, this allows for a dodgy dimmer that occurs throughout the show, as I said above you cannot adjust things like this on old dimmers without ripping the things apart, and it's not often that you have time for that!
Richard