Ill be completely honest with you, and this is just MY personal experience. Before these last 2 weeks I have been maxing out my protien drinks every day since I started program in Nov 2010, and I have constantly for the most part lost 3-4lbs a week. well...for the the last 2 weeks I have stopped buying drinks completely, and I have contunied to lose 3-4lbs in a week.
I flat out asked my center is the drinks will slow my weight loss down their answer was "The drinks are only in place to keep you from losing lean muscle". So take that as you may, for me, they did not change my weight loss by stopping taking them. I am going to contunie to not buy them because I am tired of giving them $100 a week for drinks that in my opinion, don't help me lose anymore weight.
But again, this is just my opinion

from my personal experience