I've run a Winwood carbon cyclocross fork on my Crosscheck for at least 3 years now.

http://www.winwoodbike.com/muddy.html

I bought it because it was nearly a pound lighter than Surly's steel fork - if you can believe the manufacturer's spec's, that is. Anyway, at first I was really careful with it, not knowing if it would take the abuse a steel ford can. Now I don't hesitate to jump it off curbs. And it has certainly run through it's fair share of potholes and other bad pavement, as well as a fire road which was part of my commute for a while. However, I don't know how it would fair running over curbs or traffic islands. But then some alloy or light weight steel forks might not fair so well their either.

DanO