Most of the time when someone comes up with a device that is just a specialized version of something you can rig yourself from stuff you already own, it's just not worth paying for. This is not that.
The Metolius PAS allows a fast anchor tie-in merely by clipping in to the daisy-chain. The multiple loops also make it useful for equalizing anchors in a safe static mode to eliminate risk of shock-loading.
Another use I've found for the PAS is for crevasse rescue. The person not in the slot can drop it over the lip to aid the poor slob who has to work up and over. It works like an etrier and the climber can simply grab the loops hand-over-hand.