Depends on the quality of the coffee for me, and my coffee purchases are on the cheapo side these days. I used to drink the good stuff black, now I add something like 1/2 teaspoon of sugar and that will take refilling/topping off. Takes the edge off of miserable coffee.
Being a Lipton's tea child (no milk), I was late, as a teen, to learn to drink coffee, since all my elders or peers wanted me to add some kind of milk to it. Yetch. It turned out to be the milk I didn't like. I was one of those kids who had to sit at the table until I finished my milk. My mother nearly force fed me really icky calcium discs... (poor me).
I didn't learn to easily drink a glass of white milk until they came out with skim, whatever that year was. I finally learned to drink coffee black at the hospital I worked at after school classes - I saw other people doing that.
Years have gone by and I have changed. Yetch to skim milk, fat is needed for vitamin D absorption. Plus, I'm not chubby anymore and some fat on the body is a good protectant. We all have our nutritional views, these are some of mine.
I got used to caffe lattes in italy and am predictably ms. picky about my lattes - doppio and no damned milk foam on top of the milk, please, and no sugar at all. I'm fine with the bit of brown foam that comes with a correctly served espresso, and the dribbles of foam on a macchiato, a mere breath. Oh, and I'll add some sugar to straight espresso. Not like some italians. I remember going to a famously good coffee bar in Rome and they put the sugar in for me (yaaaack! four spoonfuls fast!). I learned how to control that, politely. Plus, that was only that one place.
I've also turned to almond milk or coconut milk, though I will still buy half and half, to have around if I want to make gelato, or my faux Alfredo sauce.
On stirring, it is my opinion from my own non-double blind testing efforts that baking cocoa powder stirs more easily into a little water first and then almond milk than doing the same with cow milk - this being for smoothies, not coffee related,
This could be fantasy.
One more thing, maybe from that first italy trip or maybe not - it might have also related to my reading - I got used to eating way less sugar than I had before that. Came home to find bakery goods, etc., all too sweet back in Los Angeles.
Stay tuned for "As The Coffee Mug Fills".