That's funny; I stumbled across this the other day while attempting to get out of a desperate situation. I had the misfortune of saving the game at the precise moment that two skeletal elephants decided they would follow my fisherdwarf straight into my fortress.
I set the elephants' speed to some ridiculously high value--enough to where they became an (intimidating!) part of the scenery. Then my dwarves just danced circles around 'em.
Of course, it was a somewhat deplorable approach, but I wasn't in the mood to start all over again.
In regards to the attribute's influence on dwarves, I found that it does indeed affect dexterity-ascendant tasks. When set to zero, my legendary miner cleared out a 10x10 area in twenty seconds. My dedicated wood cutter completed his remaining designations in a couple of minutes (about 20-30 marks). Faster, indeed!
[ September 09, 2006: Message edited by: Nilas Hadean ]