the first bodybuilder I ever saw was at a campground when I was about 12 years old and he used to walk around everywhere with a gallon of milk, and he was constantly drinking it. This guy was jacked and had very low bodyfat.
I believe milk is great for putting on weight if you are a hardgainer, but should be avoided by those needing to lose weight like myself and I love milk. Plus sometimes it doesn't agree with me.