Probably person and climate specific to a degree. You might want to experiment with a less expensive item first to get a sense of it.
Gilets and vests are not super practical in my climate except in the transitional seasons. But I'm soon moving to a climate where they are more practical.
I do think they can work brilliantly indoors for many.
The other place they truly come into their own is in active outdoor pursuits. It's so great to have your arms free of restrictions if you want to swing them as you move. So they're fantastic for hiking, skating, snowshoeing, cross country skiing and the like -- or even just for brisk walks. You do have to layer of course. But a warm sweater or windprotecting garment or leather jacket or fleece or even blazer with a puffer vest is a lot warmer than you might think. You can also layer that type of puffer under a trench for added warmth.