i used to drink skimmed milk but someone pretty reputable told me otherwise just last week.
after working out, there is a 36hour window during which your body needs protein. by taking skimmed milk or whey protein, your body absorbs it instantly, which is good immediately after working out, however those meals with fat, e.g. full cream milk are better in the long-term since the fat slows the absorption of the protein.
i'd say milk is all good. no acne related stuff. i'm drinking about 1500-2000 litres a day just now.
obviously don't rely on milk as your main source of protein. you have meats and fish for that. what also helps is nuts. high protein and high fat, hence your body will absorb the protein slower, which is very good for during the night. so whenever i go to bed i eat about 30-50g of peanuts with milk.