I'd be happy with some "nutritional" information alongside the usual app info. If I'm trying to choose between several note taking apps for instance (assuming they both claim to deliver a similar set of functionality) I might just go with the one that's not going to hog all my memory or drain my battery. Like nutritional labels on food it won't be completely accurate, but at least I'll know to choose the crackers over the chocolate cake if I'm trying to lose weight.