A couple of weeks ago I went to run barefoot on a rubberized track, and I barely made it 1/4 of a mile. Today I made it 3/4 of a mile on the same track with a little "sprint" at the end. I probably could have gone further without too much trouble, but I decided not to push it. Also, 3/4 of a mile is my longest barefoot run since I've started barefoot training. I still can't do much barefoot running on the cinder track, but I'm walking on it now without too much discomfort. With any luck, I'll be able to run on it soon.
When I run barefoot, the surfaces hardness is pretty much irrelevant. However, the texture of the surface is the limiting factor. I think my experience is pretty typical for people who have good enough technique to land on their forefoot.