I do, but only because I have tiny bantams of a breed not known to be cold hardy, and because we get such crazy temperature variations (70's one day, below freezing literally the next day), our poor chickens never get the chance to acclimate to winter temperatures.
However, even with our weird weather, if I had standard size chickens, I wouldn't add supplemental heat. I would just make sure my flock had a dry, draft free but well ventilated coop to cozy up in with their natural down insulation.
No heat here. I live in southeast michigan and temps have gotten down to 0 and I haven't used any heat and the chickens are fine. I have RIR, Leghorns, and EE. They are even outside in the 0 weather in a covered run.
Two, 250 watt heat lamps attached to a thermocube. They don't need it but it makes me feel good when it gets to -20 outside. I have an uninsulated 4x8 coop and it has gotten no colder than 5 degrees in the coop.
Wisconsin here:
No heat, no extra light, but we do have a water heater.
I keep it so cold in our house we have to crack the ice in the toilet most mornings.
No heat. No extra light. The heated water is in the run. It's gotten down to -7 here a couple of times. I open the pop door into the run almost every day, except during 2 really bad snow storms. I do take in fresh, warm water every morning.
We use a ceramic 250 watt bulb that plugs into one of those metal clamp lamps. I have a good sized coop and I want them to be comfortable. I turn it off during the day and try to only use it when it is super cold out. I also use a heated dog bowl for their water.
This is it -- it doesn't put out any light at all and you can get them in smaller watts