I only had one flight attendant question me about it and i've used it about 20 times. But the one that did question me about it was VERY VERY rude, insisted i couldn't use it for take off and landing (as though it would be safer for a 2 year old to just have a regular seat belt? wth). I took out the little booklet they gave you with it and showed her the faa regulation and she took the booklet w/ her to try to argue to the captain of the plane that I was wrong, but he disagreed, showed her the regulation and then she let me put it on.
Asside from this one evil lady i believe it was a north west flight everyone else has thought it is very neet and some of the flight attendents ask how it works so they can get one for their children.