It seems to me that some don't fully grasp how the fast idle actually works. The rpm, in fast idle, as I understand it, is CLOSELY controlled by the governor. The governor applies and subtracts throttle much much faster that a human could if he were standing at the engine with his hand on the throttle. Add in the delay associated with the throttle linkage, and air throttle is much quicker than cables or rods, and you end up with a somewhat hopeless situation of "lag" in injecting corrections and you end up with a over revved engine that is frying the clutch or you stall out. The process has you engage the clutch at the absolutely lowest RPM and in the shortest time so as to not fry the clutch. You use the closely controlled "governed" fast idle to just get things hooked up and then, because fast idle will not apply full throttle, you switch out of fast idle and then depress the throttle to get WOT. Wallah! "Huston, we have movement that doesn't involve Exlaxx."
Now, this is just my grasp of things having heard them in various levels of detail over the years. Please correct me in any way for the sake of those others that don't really understand. God knows that I shouldn't have the last word around here.
If you don't have fast idle and you have a stick 4 or 5 speed you would benefit from get it installed. If you have it and it is locked out with the handbrake or any other mech I would suggest you modify your system. Bus companies often hired less experienced drivers and everyone needed protected from their rookies. We have a lot of safty systems around us that "Real Men" don't need to be successful with the ladies.