i drink between .75-1.25 gallons of milk every day, and have for years (when i'm to lazy to cook or eat sometimes it's my primary kcal source)... and no acne. usually whole milk too.
there's a good 3000+ kcals in a gallon of milk... and it tastes good. what's better than a box of cookies or a bagel w/cream cheese and ice cold milk? i even drink milk with pasta or cheeseburgers rather than soda or juice. on a hot day (i live in palm desert where it's 115+degrees summertime) i'll even guzzle milk before i guzzle water, juice, or soda.