Has anyone here used one of these?

Our daughter is now 4 and she has a 16" bike that she rides to and from school everyday on training wheels.

In this country there are bike paths everywhere and we don't live that far from the city center so in the warmer months we spend more time on bikes than in the car.

I saw this and thought it would be very handy to teach her the rules and such as well as riding basics and still allow me to take control when she is too tired or we are in a busy area.

Reviews seems pretty good but I'm curious how they perform under real world usage.

Bike shops were of no help in this because all they sell are what they call tag-along bikes which is essentially the rear half of a bike on a bar so it can't be disconnected and ridden independently like this can.

I have put this here since it is technically a parenting question since it involves teaching our daughter how to ride a bike.