Short answer: in 95% of cases i’d say no.
Long answer: it’s an okay tool that is overpriced
So you probably already have some sort of personal tether device which you decided to buy. If it is a PAS, well, okay cool. Now I think it’s pretty safe to say you will want to use it everywhere and are now a personal anchor aficionado since you put a incredible amount of money on a sling sewn to a sling. But, before you start wearing it out and using it in all sorts of dumb situations, let’s talk about time and place.
There should be no reason to bring these things to the sport crag. Unless you have a crag that requires you to lower due to only having bolts at the top, i see no reason to use these foolish things. You can easily follow one of the ways to do it without a daisy chain, personal anchor or PAS which are just as safe as the PAS.
Again: I would consider bringing it when I know that I might be in a situation where i need to clean and then rappel. If not, if you always lower, leave this thing at home. Using a sewn sling or a piece of cord is much easier and cheaper if you have to do this.
Multi-pitch climb that tops out
Again, there should be no reason to use this things on a multi-pitch that tops out. For every anchor you can easily just clove hitch yourself to a draw and then build an anchor with this.
If you’re just going to stay tied in, then there is no reason to not use the rope this way. you are, somewhat, connected to the anchor, but your strand does not have to bear weight. In this case, especially if you top out, you will never need the PAS at any anchor and can easily make up a good way to rappel if needed using slings.
Multi-pitch climbing that doesn’t top out, rappelling
Okay, so here i might want some sort of device that would make stances really easy and simple and quick. obviously, using a sling will yield different lengths from the anchor than the ideal stance. That’s why here, i usually opt to have something like a daisy chain or a PAS. However, know thy equipment and treat it the way it deserves to be used. Falling, even a short fall, on a PAS can break you and destroy an anchor (they are not dynamic) and can rip open loops on daisy chains. That’s why i always ere on the side of caution and put my weight on these things.
However, you can always do this to shorten a sling: tie a knot where you want to tie in.
In this case you see the person using the knot to limit where the ATC will go. You can do this with a PAS but a sling is fine too and works well in other ways that a PAS cannot emulate. plus it’s easy, light and going to be on your rack anyways.
So should i buy a PAS?
I don’t think so, but do what you want. Just make sure you know what you are doing and aren’t buying safety gear because someone told you to.