At some point I have a feeling that here is a splitted discussion between backward flight transition (than can be usefull in certain condition) and circus flying and opening beer bottles with helicopter...
Are the pilots flying in Red Bull race best FW pilots in the world? If so, than rearward AR is essential thing in every heli pilot training.
If not - than it is good to know that it is possible; essence of flying helicopter is to do your job safely and correct with high enough safe margin.
That is my opinion. Doesn't mean that I wouldn't be able to do something simillar in helicopter like this. But, at the end of the line, good pilot is living pilot.
Mike