I have a 780 with high speed rotors and am running with a 780 that has regular speed rotors and I am getting at least a 20% capacity increase in cereals(more when it's tough). It is to the point where I would pony up the 12K per gearbox or whatever they cost if I didn't already have them. Should be standard equipment on all models, not just 780's. The extra rotor grates have much less impact on separation ability than the speed.
Just what advantage do you see with the high speed rotors? Is it more throughput, less loss...?
I often see little change in my crops with rotor speed.