Actually most of us who run barefoot find urban environments drastically easier and more comfortable than natural surfaces. The reason is simple. When your form is good, the hardness of the surface matters very little. You're generating less impact, and you're absorbing it with the muscles and tendons that are built to absorb it (mostly arch and calf).

It is sharp and irregular surfaces that are difficult to run on barefoot. Natural trails are very difficult for me, but I can easily run 11+ miles at a time on pavement barefoot, and I routinely do.

I ran the Boston Marathon yesterday in Vibram FiveFingers, which are like thin gloves for your feet. My marathon recovery is faster now that I run barefoot & nearly barefoot than it was in my shod days.