Not done it, but a buddy and his wife (experienced horsemen) said it was one of the most terrifying things they'd ever done. Instructions were to look at the wall if one felt insecure.
Standing on the rim the day before, I was a bit queasy looking down and was some what anxious about that. At my age I get nervous at the 2nd step of a step ladder. After the first 50 yards on the trail looking at the trail over the mule's ears, I was good. In a mile,I was looking over the edge and marveling at the engineering feat of carving that trail without modern day machinery.
It is not a trail for the faint of heart.
