I can't think of why it wouldn't be a good thing. Cold winds and cold weather can dehydrate things pretty easily, so I think deer would benefit from a reliable water source.
I do know that the farmer from who we bought our place had a year round water tank for his cattle and he would mention that he'd often see deer using it. We've also got an ice free water source at the bottom of the dam on one of our ponds. Not sure how it works, but we do see deer tracks around it in the snow.
“There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery, and the other that heat comes from the furnace.”