I can't talk about the science behind it, but here is my opinion. Take it for what it is worth.
Flat out, I don't think it will make or break you...GIVEN THE REST OF YOUR DIET IS CLEAN. I think everyone needs a couple things they "plan into" their diet so they don't go bonkers. If you are on a clean diet, then 1/2c milk a day probably won't be the reason you don't meet your goals. BUT, if you are NOT eating clean, that is a different story.
Also, there is a dramatic difference between someone who wants to comete, who wants a 6/8-pack, who wants a fitness competitors body/definition. If you want one of those things, then I wouldn't drink the milk. It is sugar. If you are someone who wants basic definition, flat-ish stomach, solid legs, etc....then it will probably be fine.
I have come to accept that if I eat clean 95% of the time, I can plan in somethings that are not clean (i.e., small low fat yogurt, such as Yoplait). This will not keep me from my goals. BUT, I have also dramatically altered my goals and expectations fo rmy body and myself over the last 6 months. I no longer wish to compete, I'd rather just look healthy and fit.
I think it takes examining your goals and expectations....do you want to lose the weight faster? Don't drink the milk. Can you give yourself small "treats" without going overboard? Then drink it.
The mroe clean your diet, the faster results will come and the more dramatic they will be. WIll you get there drinking milk? Probably, it just might take a lot longer.
Test it and see.....stop drinking it for 4-6 weeks, see if there is any difference.