We use out water system in the winter, but it takes some care and depends on just how wintery your winter is. If your are talking about using it where the highest temperature will be significantly below freezing, then it is probably not worth the risk. However for desert SW type conditions (think southern Utah, Nevada, New Mexico) where it is typically at or a bit above freezing during the day, then it works pretty well.
There is no issue at night with the furnace running and the hot water heater warmed up, if it is going down to the single digits we will also open the cabinet doors. If it is at or just below freezing during the day, we will heat up the hot water tank in the morning and leave it on, which provides a bunch of heat and thermal ballast to the cabinet where the plumbing is. You can also heat the water heater, and dump it back into the water tank, which will keep that nice and warm for many hours.
I also have an on board air compressor, a blow out fitting and an empty jerry can. If it looks like if we will hit really cold weather, I can fill the jerry can from the camper tank (to still have water), then winterize the camper with the compressor in about 15 minutes.