Here’s an old topic regarding this:
Jeff Hammond & Robb make some good points there which I tend to agree with, though some can be solved with the use of voicerecord-aliases/macro’s. (I find the idea of being able to make your own language that controls Rhino amusing)
I imagine the fastest workflow would be a combination of voice recognition and typing though. But I think we’re still far away from that. And in reality I think I would prefer just using the keyboard with my shortcuts set up instead of bothering colleagues with me talking to my computer. (I guess multiple designers sitting next to each other might need some sound insulating cubicles 
)