I would also add, if your violin is not new-ish, the peg holes might be reamed out a bit. The perfection pegs might not fit properly unless the peg holes are "resurfaced". Not all peg holes will have worn the same, so its possible you might have to mix/match the 2 sizes they come in.

I can see a need for them with some arthritis or weaker hands. At this point in my life, I'll stick to just using friction. I only have 1 fine tuner on all my instruments, except the electric. It might be a skill set lost sometime not to far into the future.