Personally I would not waste my time or money on this. If I was under 10 years old I am sure I would love it, as I am sure I had a similar whistle when I was a kid.
The first thing that puts me off is the fact that the fan blades are turned by impeding the airflow (the way all passive fans work), so therefore it actually reduces the airflow (at least initially).
Some energy (your suction) is wasted in producing that silly sound too.
Just seems like a big gimmick to me.