Some thoughts:
Remember those of you that consider using heat--what is going to happen if the power goes out? If the chickens are used to the cold, nothing, but if they haven't adjusted there may be a problem.
Frozen eggs are always a big problem. Gotta try to keep them picked up...
There is a post on here someplace from a member in Alaska who uses no heat and her birds are fine. Just remember when you add heat you're introducing a source of possible fire so unless it is absolutely necessary, why do it? BTW, my aunt, who lived in Blackduck MN had chickens for years and...
You guys that are using heat lamps are playing with fire--literally--we've had 3 coop/barn fires locally from their use in just the past couple of years. I'd think two or three times before using them since, aside from keep water from freezing, they probably aren't necessary to your chickens...