I was curious about those too but wary about buying a whole box and not liking them, why can't shake people do like test packets so we can buy just one ?.
IMHO - Anything that makes dieting marginally more interesting should be cheered and celebrated
My only concern would be that the shakes are quite far away from the wholefoods and natural end of the food scale. I know most of them contain Vit &Min additions, protein, carbs etc but most of these are synthetic additions and what about all the other bits that our bodies need like antioxidants, fibre, amino acids and other trace elements that the chemist didn't think to add ?.
On saying that we live in the real world and while I happily munch on my pepitas and goji berries I'm also drinking a Pepsi Max
So - if it fit's into your diet, doesn't make you feel bad and it tastes good go for it