I shoot 1860 Colt (Pieta) conversions. These revolvers have a much shorter "stroke" on the hammers than my NMVs and I find I'm much faster because of this.
I know folks with a bit or arthritis and they have a hard time pulling the hammer all the way back. This will be a great modification for them.
And if you are "ham handed", the hammer will stop on the web of your hand and you will "short stroke" the revolver and it won't go bang!
Plus this kit removed the hammer transfer bar, this is a huge improvement in lowering the hammer spring rate and still getting reliable primer hits.
Except for the "Rolex" price of these kits, I can see no reason to not install them...............