Since I am making my workbench top out of Euro Beech I thought it would be interesting to make the base from the quintessential Southern hardwood, Hickory. When I was checking out the hardwood at my supplier they suggested the Beech. Once I saw it and the predictable grain that Chris refers to it just looked easier to work than the grain in the Ash, the other hardwood I was considering. Plus I have a compact Hammer workbench with a German beech top that I have been very happy with.
Right, Hickory is flexible in a handle as compared to steel, iron or other very hard wood like hard maple. Even in steel the knife guys talk about tough steel vs hard steel. A steel that has a little "flex" in it stays sharp and often makes a better tool than steel with a very high hardness that ends up being brittle under certain pressures. In the 5 3/4 x 3 1/2" legs of a bench I think Hickory will be a very sturdy base. I suspect it might be a chore to flatten a whole bench top made of Hickory though. Maybe a little more test than I want to give my recently made Purple Heart planes, even with my HNT Gordon HSS steel iron.
Here is Roy's Hickory video. I think since it is educational it is ok to post the link:
http://www.pbs.org/woodwrightsshop/video/3100/3103.html