When considering the usability of a design, the two factors that should be taken into account are WHERE the product is going to be used and WHO is going to use the product.
Take into account a marble messaging machine, that shows the amount of phone messages you have represented by physical marbles. While this design is aesthetically pleasing and user friendly, it would be best suited in a home designed for a single person/family rather than a hotel setting where the messages aren't personalized .
