I too am a fan of rapid prototyping, but the example app here is incredibly simple. More complex apps require more time to refine & prototype. That said, this

I too am a fan of rapid prototyping, but the example app here is incredibly simple. More complex apps require more time to refine & prototype. That said, this sort of flat prototype should be do-able in a few days for even the largest of apps. So, I'm in agreement with OP — except on the timeframe :)