"Drinking unsupervised milk causes agnosticism. The milk may in fact be 100% from a kosher animal, but if no Jewish person was present to watch the milking, it has the effect of casting doubts in our core beliefs."
I have written here before that I hold like the poskim who say that 'chalav stam' in most countries IS, in fact, cholov yisrael. However, since making aliyah, I have been consuming, by default, pretty much exclusively cholov yisrael in the sense that most people use it. It has not improved my faith.
My father recently returned from a trip to the U.S. with a serious haul of milk chocolate. Earlier today, I had my first Hershey's Peanut Butter Kiss.
It was absolutely divine.