First, a note about steps
Petzl calls this a 7 Step aider but it is the same length as the Metolius 5 Step Aider. This is a good length for harder aid. However, for walls with a lot of free climbing, we prefer an aider with one fewer steps because it is less bulky and lighter when clipped to the side of the harness. Since Petzl does not make a version of this with one fewer step, we just cut off the bottom step. We've never regretted it. To learn more read our Aider Buying Advice.
This aider has the highest comfort-to-weight ratio of all the aiders we tested. It uses uncommonly lightweight webbing for most of the aider, which keeps the weight down. It uses a reinforced step that is 1.75 inches wide, which adds comfort. Of all the etrier-style aiders, this was one of the easiest to walk up, perhaps only slightly less easy than the Metolius 5 Step Aider. Excluding super-lightweight alpine aiders, this is the best standard size aider for free climbing. It is not only light, it is also very low in bulk for its comfort level. When clipped to the side of your harness you don't notice it nearly as much as you do with most standard aiders.
This aider has held up exceptionally well. Only after 10-plus walls has the stitching slowly started to go on some of the steps. But if it takes 10-plus walls for your aider to start to show signs of wear, you are winning. Like most (if not all) Petzl products, this aider comes with a 3-year warranty that should give you some peace of mind.
One unique feature is the Petzl String, which is an not intuitive name for the piece of rubber that you commonly find at the end of Petzl Spirit Express quickdraw. It protects the carabiner attachment point from wear. It also gives the aider a nice solid feel when clipping it to a piece. You can always take the sting off if you don't want it but I keep it on. If it wears out, you can buy a new one. Mine finally broke after about 20 El Capitan routes… so very durable.
The main dislike is the price: it is about twice as expensive as most other aiders. Other than that, the dislikes are more picky and are centered around the top step. If the top sub step were just a little higher it would be as good as the best aider for top-stepping: the Metolius 4 Step Aider. Also, the double grab loops are awkward. It would be better if they had just one that was big enough to slide your foot into. While the double top step is nice, we would rather have a double step for the second step where you spend most of your time standing. Or no double step at all and have a sub step on the second step.
This is our go-to aider for walls that are 50-75 percent free such as The Nose, Lurking Fear and Moonlight Buttress. It is comfortable for standing around in but also light enough to be unnoticed when clipped on the side of your harness. As mentioned above, we prefer cutting off the bottom step to lessen the bulk.
At $69 this is by far the most expensive aider. If you use it a lot, it is worth the price because aiders are among the most-used pieces of big wall gear.