If your product is something that will be used strictly in demos, do this.
If your product is something an customer will use, demo-driven development will poison your processes by creating an endless backlog of neglected post-demo stuff.
one of the most enjoyable projects i was working on was where a customer came to us with a complete and functional demo and our job was to make it work with an actual backend. and as it happened i already had a complete and functional backend, so all we ended up having to do was to add APIs on both sides to tie them together.
If your product is something an customer will use, demo-driven development will poison your processes by creating an endless backlog of neglected post-demo stuff.