I have a Hit-Air YS in Hi-vis, I think they do it in black too. Had it 7+ years.
Mine has a collar that supports your neck and a lower section that pops down over your coccyx which the one in the link doesn't seem to have (maybe it is just packed differently).
I quickly started to feel naked without it, the only time I don't wear it is on the very hottest days in city traffic because it is another layer that adds to the heat. On fast roads I always use it.
Clipping onto the tether line becomes part of your start-up routine.
They take a lot of force on the tether to fire the pin, accidentally catching it isn't going to set it off.
Fitting the fixed tether is a bit tricky on a scooter because the frame isn't accessible. Mine passes under the seat and it attaches to the helmet lock bracket (B400)
I tried it through the vent under the seat and that worked well but the line was tight against my inner thigh and bugged me. I thought about adding a second line to the same clip coming from the passenger grab rail wich would make it fire a little bit quicker in a head-on.
The tether needs to be under slight tension, you want it to fire as soon as you part company with the bike.
Once fired, they don't stay inflated, they aren't perfectly air-tight so that they cushion you but don't bounce you and slowly deflate if there is no impact. It doesn't restrict your arms when it goes off.
There is an optional chest plate.
I have never deployed the vest in anger but have spoken to people who have and said it did its job - these were bruising, bone-break offs rather than mincemeat events. Lots of bruising to limbs but none to torso.