I think the mistake that most people are making, is to just add the protein shake to their diet. Whereas it supplies valuable nutrition and protein, it still has calories.
I make mine with fruit, yogurt, milk or juice and it always is over 300 kcal. I eat 5 to 6 meals and eat as clean as possible (I also read Tosca Reno's Eat Clean Diet, I don't stick to it 100 % though - some of it is too strict for me), however, protein shakes are a meal replacement for me.
I think they are awesome for breakfast, or if I run short on time for lunch or dinner, and probably would eat junk otherwise. They are easy and fast to make, works well for me.
Carola