rhm

I have not. To be clear, I'm just not in the market. I had a custom frame made, and I'm happy with it. At the time I insisted on cantilever brakes front and back, but were I doing it again I would go with disc brakes on the rear; and this opens up options that are not fully custom, and therefore cheaper. I'd still insist on rim brakes in front, which most likely means a custom fork.

the reason for rim brakes in front is that a fork made for disc brakes has to be built much heavier and stronger than a fork for rim brakes, and I assume the disc brake fork will result in a less comfortable ride. I don't know, but perhaps the fat tires will adequately compensate for that; i think it's a fair question. At any rate I gladly confess a prejudice against disc brakes. I really don't know whether it's justified.