My X started out as a Kona Fire Mountain, First time I had disc brakes in approx. 6 yrs. adult riding.
I love them, definitely a plus.
As a matter of fact that is why I didn't use the Univega (vintage unknown, purchased at a yard sale)as the donor bike for the X. If I could find a 1" steel fork w/disc mounts I would go ahead and build another X.