The Petzl Quickstep are some of the best aiders you can get in this style. I am generally not a fan of this adjustable kind because you can't lead with them efficiently. However, these are so light that I may consider using them as jugging aiders in certain applications, such as speed climbing. I just used them on a one-day ascent of Mt. Watkins with Tommy Caldwell and was pretty impressed.
Overall, they are a specialty item only suitable for experienced wall climbers who climb walls fast (and even those climbers may not want them). The main competitors are the Yates Speed Stirrup, which is much heavier but more comfortable, and the Metolius Easy Aider, which is a little heavier and more bulky but also more comfortable and a hair cheaper. Overall, I lean toward the Petzl because the whole point of an aider like this is to be as light and streamlined as possible.