This is interesting, because I've heard at Apple you don't demo anything that is not as polished as you can make it. E.g. layout perfect, no "Lorum ipsum" text, everything must be thought-through and a realistic example use case.
"The best way to make sure your product meets the needs of your target audience is to expose your designs to the scrutiny of your users. Doing this during every phase of the design process can help reveal which features of your product work well and which need improvement."