I didn't 'install a kit', but when I ordered a Corbin seat, I asked them to provide it with seat heating.
It's a nice luxury to have in cold weather, but I recommend that if you are looking to 'add warmth' to your rides in cooler weather, you prioritize things in the following order:
1) Heated Grips - these make a huge difference.
2) A heated vest to wear under your riding gear.
3) Heated chaps to wear under your riding gear.
4) Heated gloves.
5) Finally, a heated seat.
I don't think a heated seat would do much for you in the absence of the first 4 items. But it is a nice luxury to have once the rest of you is warmed up with the first 4 items.
Michael