From one website:

* The trail is indeed steep. The gradient is around 900' per mile for nearly 2000' of altitude from the top of the trail to just above the bottom of the Supai. This is significantly more than the 700' per mile of the Bright Angel, for example.

* The trail is relentless. There is only one very short break in that 2000'.

* It requires considerable alertness to stay on the proper trail. In many places there are several nearly parallel trails. At their intersections, it is easy to jump onto an alternate trail, leading to difficulties. Only the proper trail keeps you from climbing over boulders or having to face a dry waterfall in the streambed. All of the comments about facing such obstacles come from people who have missed the trail!

* There is loose footing in a few places, unlike the corridor trails. Although this is not much different from most of the other non-maintained trails in the Canyon, if you are not used to trails like this, you won't like it.

* About one mile of the trail is along virtually the top of the ~500' vertical Redwall cliff. That is, for one mile, any slip off the trail is potentially deadly. Fortunately, nearly all the trail is good enough so that one isn't worried about the dangers of the trail. Again, this is not much different from many other places along other non-maintained trails.

However, there are two points along that section where the trail becomes poor, with the tread of the trail not horizontal, making it tricky to navigate safely. Fortunately, the tricky section at each of those two points is only 6-10' in length, and can be traversed with quick steps and a prayer. It would also probably be easy to do a bit of trail maintenance in those locations and eliminate most of the danger if one was willing to spend the time rather than just zip over those points.