At first glance this aider does not look comfortable. However, once you stand in it for a while it is surprisingly comfortable given how skinny the steps are. Like its big brother, the Metolius 5 Step Aider, it has the Biothane step stiffeners that keep the steps open and easy to get into. For example, it is much easier to walk up than the Petzl GradiStep (although the Gradistep is also much lighter). Keep in mind that although the Metolius Alpine is comfortable given its skinny webbing, it is still not nearly as comfortable to stand in as the Metolius 4 Step Aider and 8 Step Ladder.
Of all the light aiders, this is the best one to top-step with because it has sub top steps and sub second steps. This is particularly useful on a pitches on The Nose where to climb most efficiently you can use the crack with your hands and really step high in the aiders for the next placement.
We can't comment on durability because we have not used it enough to really test that quality.
All aiders eventually have the steps turn inside out, especially the bottom step. With this aider it seems to happen more often. Not a deal breaker, but a little annoying. While this aider is very comfortable for its size, it is not nearly as comfortable as the Petzl WallStep, which is about the same weight (but also more bulky).
This aider excels on a route such as The Nose or Half Dome that is 50-75 percent free. While you are doing free moves this aider is not bulky on the side of your harness. But when you need to aid, it is very capable.
This is the best value of any lightweight aider we tested. It is less than half the price of the Petzl WallStep.